Bilbo has adopted the eldest of Bilbo Baggins' young cousins, Frodo in order to carry on his legacy. Frodo and Bilbo share the same birthday. This coincidence is as good an explanation as any for the favor bestowed upon Frodo. It also suggests the element of Fate that is so important in the novel.
Though Frodo is loving, generous and kind, he has his faults. Initially, he is fearful and timid. Later, when the Ring strengthens him, he is also nearly seduced by it. Still, he has a strong sense of justice. He is not only kind and generous but also loyal. He celebrates Bilbo's birthday even though everyone is sure that the old hobbit is dead. And he sells Bag End to his enemy for a pittance, showing that he is neither malicious nor greedy.
Frodo's greatest strengths are his generosity of spirit and his power of forgiveness. He saves Gollum from being killed not only by Sam but also by Faramir's men. He is ready to give Gollum more than one chance at repentance. He believes that deep within himself Gollum is a good hobbit and that he will eventually come around to goodness. Frodo also forgives Saruman, who was once a great wizard but fell into evil ways. He lets Saruman go free even though he has destroyed the Shire. This strength is also a weakness Frodo trusts too much and faces betrayal too often.
Frodo inspires great loyalty and comradeship. Frodo tames even Gollum, who has given himself over to evil, for a while. And Saruman, the enemy, acknowledges Frodo's strengths as a leader.
Frodo is very wise and just hobbit. He is also very brave. In spite of being wounded at Weathertop, he strikes at the enemy and injures him. Despite countless hurdles, he manages to fulfill his promise and completes the Quest. He puts himself and his loved ones in immense danger so that the Shire and all of middle-earth may rest in peace. Frodo becomes a poster-child for sacrificial acts of good, ultimately inspiring many others to act in accordance with the greater good.
The quest, however, does not leave him un-scarred. He has many wounds, some physical, and some spiritual. Frodo knows when it is time to leave Middle-earth for the blessed realm and, like Bilbo, he finds a successor, someone to whom he can leave his legacy. Frodo grows as a hobbit, maturing and learning many lessons of strength and bravery. He struggles against his own evil nature, but he wins. The disposal of the Ring has given Frodo an opportunity to prove himself. The success with which he does so is what makes him a remarkable character.
Sam is so full of love and admiration for Frodo that he insists on going along in the dangerous quest to return the Ring. At first, he is more excited about seeing elves and other mystical creatures. Later, though, he is caught up in the heroics of the quest. He does valiant acts that seem inconsistent with his simple existence.
Sam possesses a unique sense of foresight and intuition. He does not trust Gollum right from the start and he seems imperceptible to the effects of the Ring. Sam saves Frodo's life several times. He shows presence of mind, such as when he dresses Frodo and himself in orc-clothes to get away from the tower. He goes without sleep for days on end so that Frodo can rest. He even gives Frodo most of the food and drink during the journey to Mount Doom, knowing his truest duty is to get Frodo to Mount Orodruin.
Sam has a clearly defined sense of right and wrong. He manages to get the Ring, but he is so strong willed that it doesn't affect him the way it affects Frodo. He doesn't lust after it and when he does get a chance to become famous and destroy the Ring, he abandons it in favor of saving Frodo from the Orcs. He keeps a low profile and never wanders from his path. When Frodo collapses before reaching Mount Doom, it is Sam who coaxes him on. When that fails, he carries Frodo on his back up the steep slopes of Orodruin.
Sam is the hope for the future. Just as Bilbo passed his legacy on to Frodo, Frodo passes his legacy on to Sam.
Gandalf is a wizard who was once passed over for the post of the head of the White Council, which went to Saruman. In the course of the novel, Gandalf is a leader and mentor to Frodo and many others. Gandalf knows his powers and his limitations and refuses the Ring when Frodo offers to him. He uses his powers only for the cause of Good against Evil and never takes advantage of it. It is Gandalf who roams Middle-earth looking for information and allying strength against Sauron. Gandalf not only saves the lives of Faramir and the hobbits, but also puts himself in jeopardy to let them live.
Gandalf the Grey becomes Gandalf the White after his fight with the Balrog. He is thrown to his death but comes back to life. Everything that Gandalf does is done deliberately and with deep thought. He chooses Sam as Frodo's companion, just as he chose Bilbo to accompany the Dwarves in The Hobbit. Gandalf is fair and wise, offering Saruman a chance to repent.
Gandalf is a reassuring presence in the novel. Every time he shows up, the tone changes from one of frantic desperation to one of security and direction. Gandalf encourages the other characters to be the best they can be. He often leaves when the situation is under control and returns only when his help is needed.
Theoden calls him a bearer of ill tidings, but that is only because Gandalf seems to know everything that happens in the Middle-earth. He is ageless and has been around for quite a long while. He seems to be in the right place at the right time and believes in helping only the helpless. Like Frodo, Gandalf leaves Middle-earth for the Grey Havens when his task is complete. His exit is graceful and poignant.
Sauron is the evil servant of Morgoth who fled from the blessed Realm to settle in Middle-earth. He is the cause of all the destruction and corruption in Middle-earth. Sauron is the one who originally forged the Ring of Power, in order to control the world.
Sauron is the principle agent of evil, commanding the Nazguls to wreak havoc in the world. He brings Sarumon under his control and enlists the help of creatures like orcs, wargs, trolls, dragons and men to work for him.
Sauron is only a servant of Morgoth. His end signals peace on Middle-earth, but not the end of evil.
Aragorn, who is also known as Strider the Ranger, turns out to be the rightful king and heir of Isildur of Gondor. He is valiant and wise, and nearly as reassuring a presence as Gandalf. He is a fair leader, even making his way through the Paths of the Dead to enlist the help of the Dead and give them an opportunity to rest in peace by helping him.
Aragorn is a close friend of Gandalf. Like the wizard, he seems to come along at just the right time, in order to save the hobbits or protect their companions. Being a true king, Aragorn has the power to heal, which he uses on Faramir, Eowyn and Merry. He ends up marrying Arwen, whom he loves.
Aragorn reveals himself to Sauron as the heir of Isildur knowing that Sauron might be compelled to act rashly upon hearing this. Being a Numenor he has a life span that is much larger than ordinary men. Arwen gives up her immortality to marry him.
Smeagol was once a hobbit living on Middle-earth near the Misty Mountains. His cousin Deagol discovered the Ring, but Smeagol murdered him and claimed the Ring for himself. Smeagol was banished by his people and given the name of Gollum. The Ring ultimately ruined him, so that he longed for it as the cost of morality.
Gollum is desperate for the Ring, like an addict in withdrawal. Even when he is tamed by Frodo, and recalls some of his former goodness, he still cannot ward off the evil lust of the Ring. In the end, Gollum actually fulfills Frodo's destiny by stealing the Ring from him. In his excitement at having bitten Frodo's finger off (thus acquiring the Ring) Gollum falls over the edge into Mount Orodruin. He is an agent of Fate. No matter what his objective is, in the end he fulfills the destiny that was set for him.
These brave and royal hobbits are friends of Frodo who accompany him on his quest to destroy the Ring. They are proud of their involvement with Frodo, and fight valiantly to help him and protect him.
Both Merry and Pippin help Sam and Frodo rid the Shire of scoundrels and ruffians. Their days spent with the Ents have caused them to grow much larger than the average hobbit, so that their appearances are as great as their reputations. They become famous as a result of their travels, and though they do not retire the Blessed Realm, their graves are laid side by side next to Aragorn.
Their friendship is unusual indeed. Legolas represents the elves and Gimli represents the dwarves. Though there is little love lost between elves and dwarves, Legolas and Gimli are fast friends. Their relationship is symbiotic: Legolas loves trees and open spaces, and Gimli loves the deep underground. Both are transformed by their friendship.