GEDCOM "GEnealogical Data COMmunications"
GEDCOM is a specification for data exchange between genealogical software programs. As transfer format there are structured text files with internal links between individuals and families. It was created and developed until current version 5.5.1 by FamiliySearch.
A GEDCOM-file contains different "tags". Each tag belongs to a special content.
List of GEDCOM-Tags.
The latest "stable" version is Gedcom 5.5. The newest draft version is Gedcom 5.5.1.
Some tags as for example the tags for godparents are missing. So every software developer creates his own tags with a prefix "_". So it is no real standard and there are still some problems.
So software developers and the society of Computergenealogy in germany are developing a higher standard and discuss agreements how to understand and implement standard in software, in particular for export and following import with other programs to avoid data loss or inconsistency. A first group started, and created an extension to GEDCOM 5.5. More information you can find in the article Gedcom 5.5EL.
Then the "Verein für Computergenealogie e.V." started a project called Gedcom-L, where German programmers of genealogical programs discussed how to transfer data in between those programs based on GEDCOM standard 5.5.1, and the made agreements to fix their results. The results were presented in GenWiki in German GEDCOM-Tag, the translation will follow in wiki-en and can be found as link from the list of GEDCOM-Tags.
The article GEDCOM-Test shows examples of GEDCOM-files created by different genealogical software programs.
The full GEDCOM-Test-article is at the moment only available in german: GEDCOM-Test