There are four main categories for zipper identification:

Tooth Type - What the tooth looks like and what it's made out of

Size - The size of the teeth (which also determines the size of the slider)

Separating - Whether the zipper disconnects at the bottom

Locking - Whether the slider has a locking mechanism that keeps it from sliding down the tape

Steps 3 - 7 go into more detail on these categories and Steps 8 - 10 outline some additional qualities (metal, reversible, invisible, dual, water-resistant, and waterproof).