If we want to animate something, we have to either change the size or change the position of our object in consecutive frames. e.g. in frame 1 our object is in position x, in frame 2 it will be in position x+1, in frame 3 it’d be in position x+2 and so on.
Another concept when creating an animation is “frames per second” or FPS. How many times do we want to change the position or size of our object per second? Movies usually use 24 frames per second. That’s the minimum number of FPS where animations seem smooth and natural to human eyes.