Motion graphics is the marriage of animation, physics, and math. When setting up key frames in after effects, or other design tool, you will have to get used to the idea of various interpolation methods such as linear interpolation.
What is linear interpolation?
It is a mathematical concept. Basically it is a method of constructing the in-between of two data points. Below is a video explaining the basics about this mathematical equation with examples.
Why is this important?
When creating motion graphics with programs such as Adobe After Effects you must use keyframes. How you adjust the interpolation between keyframes changes the look and feel of the animation.
True mastery of any skill requires a deep understanding of all the concepts that skill is based on. Linear interpolation is the simplest of multiple interpolation methods we will dive in to and one of many concepts that motion graphics relies on.