He is the pirate who inspired Luffy to go on his journey as a pirate. He found the Gomu Gomu no Mi which was accidentally eaten by Luffy.
Shanks always wears a long black cape over his shoulders and, until he met Luffy, he wore a straw hat obtained from his captain that he had worn for many years beforehand, and was synonymous with his image. He initially wore slightly loose brown trousers cut below the knee and collected halfway up the shin, with golden buttons down the outer leg. Recently he has been seen wearing a similar pair, but looser and with floral patterns on them. He wears a pair of sandals and is unshaven with a short scruffy beard.
In all his appearances so far as captain of his own crew, Shanks has worn a white shirt which is only buttoned halfway, leaving his chest exposed. Around his waist is a large red sash, which also holds his sabre on the right side. Initially, in Chapter 1, his shirt is tucked under the sash. However, in his appearances that feature him since he left Luffy's hometown, the shirt is untucked, giving him a much scruffier appearance than when he is seen in the past.
The most striking thing about Shanks is the color of his red hair, where his epithet 'Red-Haired Shanks' comes from. He also has three scars across his left eye, which were revealed to have been given to him by Blackbeard, and by saving Luffy from a Sea King he lost his left arm.
At the start of One Piece, Shanks bore a similarity to Luffy. As Oda's style changed, Shanks began to become more distinct. The shape of his eyes are drawn much sharper. His nose has become more defined, similar to how Nico Robin's nose is heavily defined from other characters in the series. His trademark red hair is also slightly longer, with his fringe pushed more toward the sides. It is also wavier and more licked back, as opposed to how it was parted in the middle at the start of the series. The scars seemed to tingle when he confronted Blackbeard.
Shanks is one of the most laid back characters in the world of One Piece, preferring to take his time as he and his crew travels around the world rather than rushing from one place to another. Shanks is not cruel like many other pirate captains, nor does he rule over his crew with fear to gain respect. His friendly nature means he will not purposely seek to harm others, and he is able to make serious characters like Dracule Mihawk join in with his fun. Yet despite how simple minded he appears at first, Shanks is a complex person with some rather difficult to understand views. For example, he believes if two people share very different views, it is better they go their separate ways.
Shanks does not seem to mind what happens to himself; he will take others throwing food and drink or spitting on him without fighting back and laugh with his crew at his own misfortunes. Even losing an arm did not bother him much. However he would never forgive anyone for attacking his friend.
Shanks and his crew are almost always seen partying and drinking alcoholic beverages whenever they make an appearance, as the captain's favorite pastimes are attending and hosting parties and banquets. According to Oda, Shanks is the one character that resembles himself the most out of all the One Piece characters, because of his fun-loving partying nature and cheerful personality.
He also is against the idea of needless bloodshed, even if honor is involved and so far seems to only step up for a fight when a friend is in danger. He also seems to admire those who have courage, as seen when a young Luffy stood up against Higuma for insulting Shanks and also when he saw Coby gathering his courage to stop the war as the young marine believed that it was pointless to continue.
Shanks also has skills of diplomacy, as shown when he brokered a ceasefire between the Whitebeard Pirates and the World Government. His skills in diplomacy are so great that he managed to convince Sengoku to agree with his proposition, even though Sengoku has a strong hatred of pirates. He also likes teasing people, as demonstrated by his apparent reactions to Luffy as a child. Oda also stated that if a child asked Shanks for a Devil Fruit he'd tease them about being ten years too young to eat one. Shanks himself was like Luffy (as a child) in his younger years.
Despite being calm and brave most of the time, he has a quirk that means his reactions are not always fitting in what others expect of him, a trait pointed out by Buggy as "always annoyed him". These include panicking when things go wrong or shrugging off Buggy's angry disposition towards him off to greet him in a friendly manner. He also seems to be carry about something personally deep within him, as when he speaks about his 3 scars to Whitebeard, he became serious about the situation surrounding Teach.
Even though he has traveled the world, Shanks believes the best sake can be found in his hometown in the West Blue. He also refers to alcohol when with Whitebeard as "healing water".
Like other characters in One Piece, Shanks has his own unique laugh, starting it with a "Da" (i.e. Dahahahahaha!).