I see it refered to and I don't get it. I asked comic book lovin' friends of mine and they have never heard the term. can someone explain it to me please?

It's the term used to describe the regular Marvel Universe.

The numbers represent the day when FF #1 was released, which in effect kicked off the Marvel Universe.

In the comics continuity, 616 is the number of the "main" Marvel Universe, as distinguished from other "alternate realities" or "alternate timelines" or "parallel universes".

Supposedly, this number was chosen to represent the main universe because it is the month and year that Fantastic Four #1 was released, which was the first Marvel comic book.

FF 1 was released in June, the sixth month of 1961. No one is sure why they didn't choose "661" instead of "616" to represent the main universe, but there are other interpretations and some speculations.....

hm...interesting. I knew what 616 meant, but not why it meant what it meant (that make any sense?). pretty nifty.

Well, from what I remember, 616 became the designation in Captain Britain, when Alan Davis was writing it in Marvel UK. He might have decided on 616 for the FF reference, but I dont think he's ever said that. It was referenced mostly when referring to our Earth in Captain Britain and then X Men after they became affiliated with each other. The Watcher started using it to describe our Earth, whe he was doing the What if series, after the Cross time caper in Excalibur. Before that he would just say things liek a myriad or alternate realaties.