This tool allows you to move a point along an imaginary line drawn between two points. Learn about vectors.

Select the point you want to move first. This can be a curve point, key point or reference point. 

Next, select the point for the vector. This means the point will be the end of an imaginary line connected to the first point. Note that the first point selected is now outlined in blue.

Enter a value to move the first point selected. Positive values will move it one direction and negative will be the opposite direction.