They're very different.
Samples are pre-recorded bits of sound for you to play back and maybe fiddle with, usually using AudioFileProcessor. Some are basic sounds like a flute or a violin and while others are bits of tunes or rhythms (these are often called beats or loops).
Presets are sets of control conditions, maybe including effects, used to set up one of the built in instruments like Triple Osc, Watsyn etc to make specific sounds.
Steve