What is the difference between incremental Rotary Encoder and absolute Rotary Encoder?

Incremental rotary encoder outputs the pulse corresponding to the rotation angle only while rotating, and is the counting measurement method that adds up the pulse from the measurement beginning point.

Absolute rotary encoder outputs the signal of position corresponding to the rotation angle by code. The Absolute position from the starting point is measured by the output code data. The position is memorized though the power supply is cut off.