You've seen it mentioned on your favorite Web sites and in practically every issue of this magazine. Thousands of family historians use it to save and swap their data. But for many roots researchers, it's one of genealogy's enduring mysteries.

We're talking about GEDCOM, of course — that ubiquitous acronym for GEnea-logical Data COMmunications, the standard computer file format family historians use to exchange information. Though most people have little trouble using their genealogy software to enter data and print reports, handling GEDCOMs can be intimidating. Fear not: Our primer provides step-by-step instructions for creating and using GEDCOM files.