Tyrone is a clone; the first complete one, created by Dipper in the episode "Double Dipper", he's also the main antagonist of said episode.
Tyrone was created by a copier, able to copy human beings. He was created to help Dipper impress Wendy, and was originally named #2. He doesn't want to be called #2, and changes it to Tyrone, the name he's always wanted. He then takes care of Paper Jam Dipper, holding him like a baby and trying to feed him a snack. After all the clones turn on Dipper Pines, Dipper fights them to the death, and uses a Party Popper to work the fire sprinkler. The rest of the Clones disintegrated when the water got on them, but only Tyrone remains. Dipper and Tyrone fight but then look at Wendy and Robbie hanging out, and they give up and become fast friends again. Up on the roof with Dipper, they chat and then Tyrone disintegrates when he accidentally drinks a can of Pitt Cola. He makes Dipper promise to not act weird around Wendy for him, and then disintegrates completely.
Tyrone is a copy of Dipper Pines, meaning he has the exact personality. He is a helpful person, but sometimes wants his own way.
Tyrone looks exactly like Dipper Pines, except that his skin is a bit more pale, and doesn't have a blue tree on the front of his hat; instead, #2 is drawn on there in marker.