A:
A trigger rod is a rod that has a little "trigger" on the handle. If you look at the picture of the handle you can see the little thing sticking out. It allows you to use bait-casting reels easier as the "trigger" gives your finger a place to hold the rod steady.
The quick answer is that a trigger rod is a rod made for baitcast reels. A Spinning Rod is for spinning reels. Hope that helps.