I don’t know what the actual definition of a kicker is
. I was thinking people used kickers from trolling but I’m still pretty new to boats. I take my son fishing on the river often and done want to get stuck down stream. It can be pretty shallow in spots where we’re at too.
Been boating since the 1950's. AFAIK, the terms are pretty universal.
A "Kicker" is a gasoline powered small motor mounted on the transom next to the main. Some people use them for trolling, with a secondary purpose as an emergency backup. Regardless of one's purpose, it's on the boat and ready to go at all times.
Optionally, some boats are equipped with an electric motor, usually mounted on the bow, and almost exclusively used for trolling, thus aptly called a "Trolling Motor". That said, though, many of the newer higher powered ones can be used for emergencies as well.
To further complicate things, "Trolling" has different meanings as well.
When I drop my kicker and set her to 1.9 mpg I throw a long line out the back with a plug on it and I TROLL for muskies. Alternately, when I'm moving along the weed beds and casting with a spinning rod, I use my electric foot pedal mounted trolling motor to move around in all different directions.
Thus, when your fishing choices vary, having a troller and a kicker on the same boat is the cat's meow.