Projection

Projection is how the hair is lifted in relation to the natural curve of the head.

Think about a protractor. If you put the protractor on top of the head and pulled the hair straight up, you would be projecting the hair at 90 degrees. If you put the protractor on the back of the head and pulled the hair straight back you would be projecting the hair at 90 degrees.
Remember to "project" the hair based on the curve of the head.

More on How to Cut Hair.