How do you distinguish Classes of Amplifiers?

[jedisteve]

I have heard many people mention they are building a class A, B, C, or D amplifier and I was wondering what the differences were...and if so which one would be best for building a small practice amp...I am hoping to build one and I would greatly appreciate the help.  Thanks.

[teemuk]

See: http://en.wikipedia.org/wiki/Electronic_amplifier
I'd say go for class-AB.