To achieve natural or believable movement, it is very important to allow what you are animating to speed up and slow down. Objects, people, animals and so forth simply do not start and stop on a dime. In the cartoon world, there are exceptions for comic effect, of course, but a good rule of thumb is to always consider slow ins and slow outs. Just like when making those infographics by an infographic company
This is simply a matter of adjusting the amount of change from frame to frame to create the feeling that something is either speeding up or slowing down. The less change you incorporate from frame to frame, the slower the speed; the greater the change, the faster the speed. This process may seem elementary, but it is often lacking in an inexperienced animator’s work. Often referred to as a sense of timing, this element is one of the most important ingredients to the success of your character’s acting.