In the context of video games, an ISO (or ISO image) refers to an archive file that contains the contents of an optical disc, such as a CD, DVD, or Blu-ray. When it comes to classic games like Dragon Ball Z Budokai Tenkaichi 3, ISOs can be used to play the game on modern computers through emulation. Emulators mimic the functionality of the original gaming console, allowing users to run games from older systems on their PCs.