In motor vehicles and especially racing, it describes the angle of the wheels ... see the diagram below, which is a top view of the chassis.
__ __
/ /______\ \
/_/ || \_\
||
||
_ || _
| | || | |
| |--------| |
|_| |_|
You see how the front wheels are "angled in"? This is called "toe in". This has some effect on the steering. It makes the car go straighter, but also increases tyre wear, and limits steering. Toe in is measured in degrees. Typical toe in is about 1.5 degrees. | 
