Working with Animations > Editing Animations > About Easing Movement
  
About Easing Movement
Easing is the acceleration or deceleration of a part or a camera's movement. You can add easing to any number of keys, and you can perform the operation on one or more keys at once. A key must have the Spline interpolation mode set to add easing. Each ease controls the velocity of the item at these points around the key:
Ease to—Approach
Ease from—Departure
The body moves according to the ease value you set:
Slow—Decelerates
Normal—Travels at a constant velocity
Fast—Accelerates
For example, when you select a key at the 5–second mark and set the Ease to value to Slow and Ease from to Normal, the object decelerates as it approaches 00:05. After the 5–second mark, the object continues traveling at a constant speed toward the location set by the next key.