Scott Lang (Ant-Man) is a character from Marvel Comics and the Marvel Cinematic Universe (MCU) and was portrayed by Paul Rudd. Ant-Man has been portrayed in comics as several alters, including Hank Pym (the original and creator of the technology), Scott Lang, and Eric O'Grady.
In the MCU, the Ant-Man films and appearances acknowledges the origin with Hank Pym and currently Scott Lang is known as Ant-Man, portrayed by Michael Douglas and Paul Rudd, respectively.
In the films, Scott Lang has become a reformed thief and was recruited to wear the Ant-Man suit. At first he is reluctant, but soon accepts this as his fate and learns to embrace his superhero identity.