That is not revealing enough. The Mac OS X has gone through 11 different versions, and it's now up to 10.10.2, which represents the second update to the latest OS, OS 10.10.0 (Yosemite).
The "easiest" way to find this out is that after your machine boots to the desktop, at the very top left part of the screen, there is a "black" Apple symbol. When you click on that, a sub menu appears, and the top entry is "About This Mac ....". Click on that, and the next screen that appears should say something like "OS X (then the name of the OS)", and under that, it should state the actual numbered version. For example, on my Mac Mini that I am entering this on, when I do that, it says "OS X Yosemite", and under that, it says "Version 10.10.2".
