GEDCOM stands for GEnealogical Data COMmunication. The GEDCOM file is a format developed by the projects and planning division in the Family History Department of the Church of Jesus Christ of Latter-Day Saints to meet their genealogical data communication needs, and the needs of other institutions wishing to exchange data with the Family History Department. GEDCOM has evolved into a de facto standard supported by most genealogy software companies and developers for the exchange of genealogy information between different computers, systems, and programs. There are several versions of the GEDCOM standard, however, and some programs won't handle older or newer versions properly.
If you are familiar with ASCII files for word processing or dbf files for databases you will understand gedcom files. If not, then consider that in the word processing business many companies were selling word processing programs using different formats, i.e. they did things differently from each other. So if you used Word Perfect you could not read a Wordstar document in your Word Perfect program. So, ASCII files were invented. All programs started to come with the ability to save a file as an ASCII file, meaning they all used the same formats so any word processing program could read an ASCII file. So, I save my document written with Word Perfect as an ASCII file, then I give it to you on a disk and you can read it with your Wordstar (or whatever) program. By read it I mean you could open it with Wordstar and edit it or whatever.
The LDS did the same thing for genealogy files. All the genealogical database programs used different formats. So, LDS established a standard file format, called gedcom. If your genealogical database program has the ability to export your records in gedcom format, you can then give your records to someone else, who can import them into their genealogical program, if their program has the ability to import and export gedcom format.
So, you use the capability of your genealogical database program to export your genealogical database records to a file on a diskette. You then can send the diskette to the LDS, or give the diskette to someone who wants to import your records into their genealogical database (as long as that someone's genealogical program allows import and export of gedcom format).The key to all this is to find out if your genealogical database can import/export gedcom files. If not, you may want to consider buying one that does (I hope you do not have too many records in your old non-gedcom capable database). If you do not yet have a genealogical database, it is probably a good idea to buy one that does have this capability. If you don't foresee using it now, you will someday.
A draft of the Mormon Church's Version 5 of the GEDCOM standard has recently been released. There's a new "standard" GEDCOM every few years. However, the situation is even more complex than multiple standards. Since the official standard has always been somewhat inflexible, every software manufacturer has felt free to enlarge the then current standard to incorporate their own features, often in ways incompatible with others who have added similar features. Thus, it is somewhat iffy to import someone else's "GEDCOM", unless they put out a vanilla version at a version level that your program will read.
Family Tree Maker (FTM) for Windows offers you several options on the import of foreign GEDCOMs that correspond to the current Personal Ancestral File (PAF) and some of the other software products. In general, I've been able to pull random GEDCOMs from others and read them into FTM with only the loss of a few "special" fields. On occasion, however, it has not been possible to read them at all - with FTM protesting that the hierarchical ordering of the GEDCOM fields it was encountering was improper. This was possibly due to someone following one of the older GEDCOM standards as their base.
Here is the URL for Banner Blue's support page for Family Tree Maker. http://www.familytreemaker.com/supptop.html
I started out using both Family Tree Maker and Reunion. While the inputting and field definitions were easier on Family Tree Maker I had some problems with the limits on the size of the output charts. Since they Banner Blue increased the size of the charts allowed but I still liked the method in Reunion where I could move the chart boxes around. I had mixed feelings on both but I got tired of GEDCOM'ing files from Family Tree Maker to Reunion for printing so I opted to go to Reunion. While the CD's in Family Tree Maker sounded exciting they didn't really give me much more information I could find at the local FHC of the Mormon Church.
If you're interested in the Reunion Software here is their URL: http://www.leisterpro.com./
The current version for Reunion is 4.0 with a 5.0 release this fall. I think they still have a demo package for downloading.