I'll take a stab at this, but will probably get tongue-tied:
Marches come in 4/4, 3/4 (retreats), 2/4 (quicks), 6/8, ect. times and are written for competitions but the timing is to march to as opposed to dance.
Strathspeys have a strong, weak, medium, weak timing and are written (traditionally) to perform a strathspey dance to.
Reels are the quicker paced dance tunes that most are familiar with if not mistaken for jigs.
These are general blanket statements, but I hope help some.

Quote Originally Posted by timber View Post
I for one really enjoy listening to bagpipes, but I am completely in the dark about what each type of tune is. Could someone explain what marches, strathspeys, and reels are?