Each Windows has it's name, like 2000, xp, vista, 7, etc, most likely so consumers don't get confused, and then they have their version numbers just like any software does.
Windows XP is technically Windows 5.0, Vista is 6.0, and 7 is 6.1.
The 7 in Windows 7 is just the name of it, since vista was 6.0 they named it 7 (at least I think that's why it's Win 7)
So in answer to your question, both Windows 7 and Windows 6.1 are the same product, it's just 2 ways of referring to it.