For example, you might create a walk animation for a character in your game. You might also create an attack animation. In your game, these animations may need to happen at the same time. Use the play buttons next to each animation to preview what your character will look while walking and attacking. The same attack animation might also need to work with an idle, run, or jump animation. Being able to play back multiple animations allows you to make sure that your attack animation works properly with all of these and that you don't have any conflicting keyframes that cause unexpected results.