Drywall is the main form of interior wall surfaces today. Inexpensive, easy to install and repair, drywall is everywhere. It is relatively durable but also easy to damage from impact or moisture. Remedy often includes cutting out a portion and putting in a new patch. The edges are then taped and sanded and repainted to make a nearly invisible repair. If you have a textured finish or wallpaper over it then the repair becomes a bit trickier.
Here are some tools and materials to help fix small bits such as door knob holes and such.