This post will explain some of the most common types of braids.
(The photos are linked to the orignal web page.)
1) English Plain
Your common school girl look
2) French Braid
Like the English Plait, but started higher on the head, created by plaiting three pieces and pulling in hair each time
3) Dutch Braid
This is like a French braid, but you plait your hair under not over.
4) Fish Tail Braid
A braid with two pieces of hair, where you bring a small bit of each over each time
5) Waterfall Braid
Where you braid like a French Braid, but on the underneath, or lower braid, you drop the strand of hair and pick up a new strand. (You can get complex on this one, and do one waterfall braid, then a second using the pieces you 'dropped' from the first braid, to bring all your hair up... I should do a tutorial on this)
6) The Twist
Start with two pieces of hair and twist them around each other, pulling in more hair with each twist
7) Lace Braid
You would do the French braid as normal, but only take in hair from one side (instead of both).
8) Rope Braid
You separate your hair into two sections, then twist each section, then twist both sections around each other.
There are many other (way too complicated) ways to do braids, but I think these basics are enough! You can play around with how you do them (crown braids, braids into buns, into ponytails, half out hair etc), and you will have heaps of different hairstyles.