The purpose of tracking is to keep focused on a certain object/ point as it moves through the environment.
Here are two videos that demonstrate this. In the first clip I select (by clicking) a point on Mini Robosapien V2's left foot, in the second one a point on his wrist. The red cross marks the position where Evo thinks this point has gone. The coordinates of this point are also displayed in the status strip.

Mask delta:
When you click on the point you want to track, Evo puts a small window (mask) around it. When the next frame comes from the cam, it tries to find an area in the new frame which is as similar as possible to the mask. If you select a mask delta of 8, the mask will have the following size. (The red pixel is the center point, i. e. the point to track.)

Select the mask delta so that mask completely fits on the object and does not overlap with the background.

Greyscale mode:
The same as already explained under 'Edge detection'.