GEDCOM is an acronym for GEnealogical Data COMmunication. It is a data standard for exchanging genealogical data between different genealogy software programs and platforms. It was developed in the early 1980s by the LDS Church.
Most genealogy management software supports importing and exporting GEDCOM data, however the standard has not been updated since 1996 so it does have its limits. It is a good way to export a family group to share with a research cousin. However, when used to move from one genealogy program to another, be prepared for a lot of cleanup work.
You can learn more about GEDCOM and how it’s used in the Ancestry.com Learning Center.