Paintless Dent Repair also known as "Paintless Dent Removal" is the removal of a dent using specialized tools & techniques to gently remove minor dents or dings.
Do you have a door ding from someone opening their car door too close to you? Did you get stuck driving through that hail storm? Then PDR is probably for you. However if the area you are looking at seems to have a crack in the paint or the paint is "broken" PDR might not be the best solution.
Dents even several inches in diameter may be suitable for PDR as long as they are shallow and do not have paint damage.