Driver TagBasic Tag
The Driver tag provides you with a quick way to create relationships between objects. Although the Driver tag is very flexible, its main purpose is to allow you to control the targets in a morph tag using your own custom controls such as sliders and 2D vector fields.
Much of what you can do with the Driver tag is also possible using XPresso. The advantage of the Driver tag is that it is easier to use, quicker to set up and it is executed faster.
Also, the tag is extremely flexible. You can control the same parameter using multiple Driver tags or multiple knots in one tag. You can assign multiple Driver tags to one object.
In the next picture, you can see how a Driver tag has been used to help create a 2D vector field that drives three morph targets.