Well, I'm a PC user, but I don't think we're really making this guy feel too welcome. There is a good chance he's simply never heard anyone use the term "browser."
- you access the internet via some program on your mac -- when you click on an icon to launch the program, there is probably a name on the icon. If not there, sometimes the name is visible on the top of the window, or can be seen in the "help."
The default Apple browser for the Mac is Safari. Other choices like Opera, Chrome, Camino, Firefox can be installed, but if you didn't have someone specifically install them, you probably have Safari. A lot of the "other" browsers have annoying little bugs, or may have "safety" features turned on.
SP accepts a variety of image types, but jpeg/jpg format is the most likely to work.