An abscess is a localized collection of pus surrounded by inflamed tissue. An abscess in a tooth is very painful and is often drained in a process called a root canal.
In the presence of bacteria or parasites, infected tissue will sometimes form a cavity where pus collects. This is an abscess, and it's one of the ways our body surrounds an infection and walls it off in an attempt to prevent it from spreading. An abscess can develop anywhere on the body: teeth, brain, tonsils, lungs, etc. An abscess on the skin is also called a boil.
