Frame per second means the number of frames there are in each second of the project. Given a set frame number, the bigger the FPS, the shorter this animation is, and vice versa.
When you are editing a project, you can adjust FPS by tapping the numbers on the bottom of the canvas. You can set the FPS in between 1 to 24. When you first open a new project, the FPS is in default set as 12.