Mac OS is characterized for being completely graphical. The command line wasn’t present as an option when booting, at least not directly.
The main architecture that Mac supports is PowerPC. Later versions started to support Intel’s architecture.
The best “feature” about Macs’ is their legendary stability on prolonged usage. That’s quite easy to achieve especially they build the OS for a limited hardware pool so they can develop and extensive test the drivers.
The latest version is Mac OSX 10.6.6 codename Snow Leopard.
Some information came from Wikipedia