One of the most common things we are asked to do is to repair holes in drywall and plaster. These are often from failed attempts at hanging shelves, or art, or are from moving things around. Sometimes bigger holes could be from an accident like bumping the back of a chair into the wall.
Even if the holes are larger, we have techniques we can use to repair any hole, crack, or mark in drywall and plaster. It usually takes 2-3 coats of drywall compound (mud) with sanding in between to get everything smooth. There is an art to getting the wall smooth, which involves using the right trowels and drywall compound, as well as proper application technique in order to have a nearly invisible repair. That is the end goal, a repair that looks like the problem never happened in the first place!