What's the difference between a Vent Tee and a Waste Tee?

I need to lower (6 inches) the drain pipe under my kitchen sink because it is to high to accomodate my batch feed disposal. I went to the store to pick up some fittings, but wasn't sure which tee to get, so I got both. Does it matter which one I use?

If you are lowering the kitchen drain, and the drain is vertical, you would use a Sanitary Tee.

Sanitary Tee

A Santary Tee Wye would not be used in the vertical position for venting. It would create an "S" trap in that position.

tees

A true "vent" tee, or elbow for that matter, will have square corners for its turns, without even the minimal sweep that a sanitary tee has.