Answer:
1. An incline plane is a flat plan put at a positive angle with the ground (assuming the ground is horizontal)
2. Work equals force times distance. And since the hypotenuse of a triangle (the ramp) is longer than the opposite side (equivalent to lifting an object vertically), the increased distance decreases the force needed to do a certain amount of work.
3. We usually use incline planes to elevate large objects. Since it takes less force to move certain things up inclines rather than picking them up, it is much simpler to move an object up an incline.
4. You could decrease the force by making the plane's angle with the ground smaller.
5. I don't know; I wasn't in your class :)
6. Ramps, wheelchair entrances, inclined rooves etc.
7. No. A plane has to be relatively flat; therefore stairs are neither a plane, nor an inclined plane.