Texas Chainsaw Massacre
Leatherface is considered to be the main antagonist through out the Texas Chainsaw Massacre series of films and comics, due to him appearing in every film so far, and he is the one who actually wields a chainsaw to kill people, so in a way he is the one who gives the franchise its name. Due to this reason he has become a horror icon, amongst the likes of other horror slashers, such as Jason Voorhees, Freddy Krueger and Michael Myers.
In the original film he once worked at a slaughter factory as a cow killer, presumably along with his other family members. In the original set of films he was never seen without one of his masks on. He was incapable of proper speech and instead simply "spoke" in grunts and howls, but was perfectly capable of understanding other people and his families orders.
He and his family use the bones of their victims and animals to make furniture.
Unlike fellow slashers, he does not come across as sadistic or "evil", more so he does what he does because he simply doesn't understand the concepts of right or wrong, or rather he has no concepts of such. Gunnar Hansen (who played the character in the first film) describes him as "completely under the control of his family. He will do whatever they tell him to do.He is a little bit afraid of them." and Tobe Hooper in the documentary The Shocking Truth portrays him as a "big baby" who kills in self defense, because he feels threatened, in the first film he shows fear when new people enter his home.
Leatherface is mentally impaired this combined with his upbringing has shaped the chainsaw wielding murderer he is. Not much back story is given in regards to his early life as a child though.
Dead Skin Mask
The character is never seen without one of his masks on, which he fashions from the faces of his victims. This is probably the reason why he has the name "Leatherface" though in the first film he is not referred to as such.
He could wear the masks due to his inability to properly express himself with speech. He wears a variety of masks in the first film, the "killing mask" the one he wears for most of the film and when he hunts people down, the "grandmother" mask, which he wears along with a different apron, perhaps when he wants to be more domestic and the "pretty lady mask" that he wears to diner along with a suit, dressing up for dinner is a Southern tradition, so it shows the character southern roots. Each mask could represent a different "mood", or personality.
Tools of The Trade
Leatherface's main and primary weapon is his chainsaw, though he also uses a variety of other weapons, such as meat hooks, knives, and hammers.
The chainsaw model that was used in the original was either a Poulan 306a or a Poulan 245. Which was made. The logos on the chainsaw were covered with tape to avoid any lawsuits. The chainsaw was also modified as well. So whichever model it actually is it was modified for the film.
In the sequel Leatherface wields a Craftsman 4300.
Part of The Family
Leatherface has quite a large family more and more members appear in each movie and in the comics.
Working at the slaughter house apparently ran through the family since, their Grandpa who is a supercentenarian worked there and was considered very good at his job. Other family members include his brothers Nubbins Sawyer (The Hitchhiker) Drayton Sawyer (The Old Man), the owner of a gas station named "Last Chance" who seems to be the eldest, the victims flesh are processed and made into barbecues and chilli, which Drayton then sells, and presumably they also eat as well, he is referred to as either "the cook" or "the old man". It is never explicitly specified what relation Drayton is to Bubba and Nubbins.
In the Texas Chainsaw Massacre two his brother Chop Top a Vietnam veteran who has a metal plate embedded into his skull, which is likely due to an injury he sustained during the conflict.
All the family seems to be mentally deranged and are totally inept of empathy and understanding for their victims. They take great pleasure in "playing with their food" before murdering and eating them.