It's no quite as the previous answer said.
If you wish to save it in order to "export" it to another Family Tree program or share it with others, it needs to be in so called GEDCOM format. (This is the interchange format used and understood by all Family History programs.)
So you need to Export, Copy or Save As (Depending on what Family Tree Program you are using) as "name.ged"
T, February 2011