Tony Masters was a former SHIELD Agent who injected himself with a sample of supersoldier serum he stole during a raid on a secret Nazi laboratory. This supersoldier serum gave him the abillity to perfectly imitate any sort of technique just by watching someone perform that technique, whether a martial arts move, learning a foreign language, or playing a musical piece flawlessly (although it didn't automatically give him the ability to read sheet music).
Unfortunately, this also gave him bouts of amnesia every time he learned something too complex, such as the martial arts style of the alien Kree race. To counteract this, SHIELD Director Nick Fury assigned Masters' wife, Mercedes Merced, to act as Tony's agency Handler as part of a secret operation designed to exploit his new ability. Mercedes then gave the amnesiac Tony Masters a new identity, assigning him missions that seem morally questionable, but ultimately benefit the interests of the US Government and it's citizens. That new identity is
Taskmaster has since received his own comic series. Along with his mercenary profession and his main role of training recruits of various villain and hero organizations, Taskmaster has also become good friends with Deadpool, coming to Deadpool's aid during some of his wacky antics. In particular, he has helped Deadpool with his nonsensical scheme to charm Black Widow by acting as a diversion, attacking the Thunderbolts head-on while Deadpool teleports to Black Widow's location and flirts with her. To Taskmaster's surprise, the scheme was eventually successful. However, he was clearly disappointed when Deadpool paid him with cash withdrawn from several ATM machines using Norman Osborn's stolen credit card.