I don't understand the difference between an inertial frame of reference and a non-inertial frame of reference. I know that a non-inertial FoR is accelerating, but what does that MEAN exactly?
google is a great place to go for general questions like this. You will find lots of discussions and examples.
One sure way to determine whether your FoR is inertial is to drop a ball. In an inertial frame, it bounces straight up and down.
If you are accelerating linearly, it will bounce away, because when you drop it, its forward acceleration stops, but you continue moving faster and faster.
If you have angular acceleration, like on a merry-go-round, when you drop it the ball will bounce away, but its direction will change, since you are turning away from it.