Incremental Encoders...
...measure position relative to it's last known position. Ideal for regulating conveyor belt position or speed.

Absolute Encoders...
...output a unique digital numeric for any given position of the encoder's rotation. These encoders work well for robotic arm control and table indexing.

Multi-Turn Encoders...
...are absolute encoders that also measure cumulative rotation. These encoders are used for screw thread position and other motion control applications.