Gedcom stands for Genealogical Data Communication. It's a means of moving genealogical data (born, died, married etc.) from one program to another. It's been standardized almost as long as there have been genealogy programs.
If you have a genealogy program on your home computer, it has the capability of creating a gedcom (.ged) that you can use to put that same data on any other program/software like Wikitree. Wikitree can also create gedcoms to move the data to other places.