This is a subject that usually applies to the 1911 pattern pistols.
The original design had internal extractors. Some makers have changed to external extractors (Smith and Sig and Kimber come to mind) Kimber has gone back to internal extractors and will replace the slide on their pistols with external ones. Apparently the Kimber externals were/are problematic.
Internal extractors run in a hole parallel to the firing pin and the extractor is held in place with the firing spring stop. Other than actually breaking, there are two occasional problems with internal extractors. 1. Improper tension. To little or too much can cause feed and ejection issues. 2. Clocking. This is where the extractor rotates a little and can't get a good grip on the brass which caused extraction, feeding, and ejection issues.
To adjust the tension it is neccessary to bend the extractor (after taking it out of the gun) to adjust tension. Not hard but many cant do it right.
Clocking is fixed by either a new firing pin stop or a new extractor.
In the 1911, internal extractors are made of one piece of steel and acts as its own tension spring. External extractors have a separate coil spring that provides the tension. The thinking was/is that external ones would be more reliable because of the separate spring. In Kimber's case this was not true apparently.
This is probably more info than you wanted but I"M BORED!