On machines running OS X, there is an Apple icon in the upper left corner as part of the menu bar. Clicking on this icon reveals a number of options. The first reads About This Mac.
If you hold down the
option key, however, that first option will instead
read System information…
Select that option to access the System Information panel which can tell you details about your hardware, software, and network.
h/t Dillon HaferTweet