Cryovac...or whatever....

Can somebody tell me what is the deal with this? The deli I used to go to would seal the meat in an airtight plastic bag...is that cryovac-ing? How long does the meat last, then? I'm talking about the shrink-wrapped meat, you know what I mean? How much extended life does it add? Now what about the Glad brand thing that sucks the air out of the plastic bag...what's that all about?

It so nice to have such a knowlegdeable group to learn from. Many thanks!

University of Georgia Extension article on vacuum sealing