What's the difference between a gum cyst and gum abscess?

Infection: An abscess is considered a swelling caused by a bacterial infection and a cyst is caused by something else. It could be trauma or genetic in origin. They are usually treated differently but require a visit to a dentist or periodontist.

About the same: An abscess is filled with pus and it is a result of an infection. Either from a damaged tooth, infected gums or a foreign body (popcorn husk). A cyst can be filled with fluid or other cells that may have inadvertently grown in the wrong area. Both should be evaluated by a trained dentist, hygienist or oral surgeon. Some require no treatment and some require significant treatment.

Structure: A cyst can have numerous causes (infection being just one) and is like a balloon--it has a fibrous tissue capsule that surrounds its contents, which can be fluid or other substances. An abcess is the result of an infection, and is a collection of pus (typically) that fills normal tissue spaces but has no lining of its own.

In basic terms-: A cyst is a fluid filled sac with a lining of cells surrounding it. An abscess is an acute localized bacterial infection. A cyst can become infected & an infection can lead to a cyst formation. I'm not sure why you asked the question & what you are referring to when you say "gum cyst"? Are you referring to a mucous cyst from blocked salivary duct or cyst in bone? - two common cysts of the mouth.