This topic came up a while ago. There was a really good link explaining the different windings including a third one. I'm sure someone will post it again, I can't remember what it was.
Wye (also called Y or star) has coils in a Y formation with the motor wires coming out the three ends of the Y. The center is a common point, but there is no wire here.
Delta (also called D or triangle) has coils arranged in a triangle formation with the motor wires coming out the points.
Wye has 1.73x lower kv than a Delta of the same wind count.
If you want more detail, a search will turn up the various discussions on the topic.