Heh. I just linked to this elsewhere; a marvelous book for learning species counterpoint is the Aldwell-Schachter "Harmony & Voice Leading" text. We used at the UW-Madison School of Music and it's amazing.
To build on the accepted answer, the various species progress like so:
First: note on note
Second: two notes on one note
Third: usually regarded as four notes on one note, but there are differences of opinion here
Fifth: basically "anything goes"
Compositionally speaking, these are all techniques used to put pieces together, but are never a piece in and of themselves, except, of course, when used pedagogically. For example, fourth species is often used to give a "soaring" sort of feeling due to the rhythmic offsets and harmonic blurring it employs. One good example is the second movement of Mozart's Clarinet Concerto in A, K622; that intro employ fourth species counterpoint.