TAS stands for Tool Assisted Speedruns. There's a huge history of gamers competing to complete games as quickly as possible. Eventually tools were created that allowed people to simulate key presses in such a way that previously impossible feats became a reality. For example, many game quirks rely on pixel perfect or frame perfect executions of button presses. Also, some sequences of button presses are simply too quick or elaborate for the human hand to reproduce. Thus, the TAS scene emerged and took speedrunning to a whole new level. It's unfair to compare a human speedrun with a TAS speedrun, so it is necessary to specify the "TAS" acronym whenever a run is shown having been created with the use of tools. Human and TAS speedruns are completely different to watch and both highly interesting.
