Apple will be pushing out the third significant update to Mac OS 10.10 today, numbered 10.10.3. Unless we had a very specific reason not to set your Mac to automatic updates, you will be getting this update pushed to your system very soon.
If you want to manually do the update, please go to Apple menu (top left corner) and App Store (formerly called Check for Updates). An App Store window will open showing you the latest updates for your Mac. One of them will be 10.10.3.
Other than the normal stability and security fixes, the big change is the new name for the photo program. RIP — iPhoto. I believe iPhoto has been with us since 2003. Apple is now changing the name to simply “Photos” to match this app’s title on the iPhone and iPad. You should not notice major changes but if you do like working with and managing photos on your Mac, you can read about the changes here.
(FYI, iMore is a leading website in the “Mac press” and a generally reliable source of information.)