To get more into detail:
Chiptunes in MOD Format usually use samples, but these are very small and looped and in most cases hand-drawn => that gives them the typical, crispy sound.
Besides them there are many tunes in exotic formats which support synth instruments. Synth instruments constist of hand-drawn samples and a set of rules how these samples are manipulated during music playing.
Some examples for exotic formats are:
Tronic Tracker (a packed Delta Music format)
is a good source if you want further information about exotic formats and/or you want to download some tunes