What version of OS X is on your Mac?
It is easy to find out what version of OS X is on your Mac, just click on the Apple icon on the left end of the menu bar and choose About this Mac.
If you then click on More Info… and scroll down to Contents and click on Software it will show more information:
Here is the official line from Apple: OS X: Finding your OS version and build information.
The OS X version numbers and corresponding marketing names are:
- 10.0 Cheetah
- 10.1 Puma
- 10.2 Jaguar
- 10.3 Panther
- 10.4 Tiger
- 10.5 Leopard
- 10.6 Snow Leopard
- 10.7 Lion
- 10.8 Mountain Lion
- 10.9 Mavericks
- 10.10 Yosemite
There is more about these on: Wiki OS X.