RE: Difference between 7mm and 7mm-08
No, it means that they are shooting the 7mm-08 cartridge, usually people don't refer to calibers as much as cartridges, they're both two different things.
Caliber, is the diameter of the bullet, but cartridge can have a number of variations.
For example, the 30-30 Winchester, the 30-06 Springfield, and the .300 Winchester Magnum are all .30 caliber, but the cartridges are different, like the casing is different, the length of the bullet can be different.
So, generally, people are talking about the cartridge, not the caliber, I say "I shoot a 7mm-08.", not "I shoot the 7mm caliber.", because people will wonder which 7mm the guy is talking about.