It's all in the fine details. As you gradually learn tricks and tips as you grow as a video editor, you will or have eventually come across value and speed graphs. Now, what are value graphs? And how are they useful?
The Value Graph Basics
To go over briefly, value and speed graphs are primarily found in applications like Adobe After Effects (you can also find them in apps like Adobe Premier Pro). They are two-dimensional graphs that represent the value of changing keyframes from one point to another. Value graphs represent property value such as opacity; Speed graphs illustrate rates of change from keyframe to keyframe.
To put it simply, these graphs show you how smooth or rough your transition from keyframe to keyframe looks. For more detailed info, PeachPit Press put together an in-depth look at how these graphs behave.
Why Is This Reference Video Useful?
Why is it useful? It illustrates how the graph behaves based on different values. Take a look at the yellow circle, see how it's moving differently in every example? For example, "Easy Ease" is a very straightforward common transition. But take a look at some of the lower graphs, some look like the yellow ball begins moving rapidly with a slow, smooth ease towards the end.
All the graphs differences, while subtle, serve a purpose in video and will be useful to look at from time to time.
in summary : v = dx/dt ; a = dv/dt
3:)