With all software listings, note that the following nomenclature normally means compatibility is limited to the following:
10.6 and up = 10.6 and 10.6.1.
10.6.x and up = 10.6, 10.6.1, 10.6.2
10.6 to 10.6.8 = all versions of 10.6 are supported.
Mac OS = could mean just Mac OS 9, or 1 through 8 and no Mac OS X.
Mac OS X = could just mean 10.0, or it could mean all PowerPC Macs running 10.0, or all versions of Mac OS X.
Mac OS X PPC = means G3, G4, and G5s may support it with 10.0 through 10.5.8, but no certainty exists which ones. Mac OS X Intel = means 10.4.4 through 10.7.3 are potentially supported on Intel Macs, but no certainty exists as to which ones.
Classic = Mac OS supported typically 9.1 to 9.2.2 within Mac OS X without rebooting into 9 via Startup Disk System Preference or Startup manager, but no certainty as to which versions of 9 are supported unless stated. Intel Macs are not supported at all. Mac OS X 10.5 not supported. Classic is controlled via Apple menu -> System Preferences -> Classic, the Classic Dock toolbar, or menubar icon. Within Mac OS X, you'll know if you are in Classic when the name of the Application appears in the upper right corner of the menubar, instead of the between the Apple menu and the File menu.
Booting into Mac OS 9: Only supported through Apple menu -> System Preferences -> Startup Disk machines that show the Mac OS 9 system folder. All G3 and G4 prior to and including iBook G3, and PowerMac G4 without Firewire 800 are supported. The iBook G4, PowerMac G4 with Firewire 800, Powerbook G4 with ports on the side as opposed to the rear behind the hinges, iMac G4 800 Mhz with combo drive, iMac 1 Ghz and up, and eMac G4 certain 1 Ghz models and higher do not support it.
Rosetta - supports PowerPC Mac OS X applications on Intel Macs through 10.6.8, but not above, and no certainty as to which ones.
Universal - Applications which run on PowerPC and Intel Macs. These may be found on 10.4.4 and higher versions of Mac OS X, though no certainty as to which
version is supported unless actually stated in the requirements.
For more definitions on these categories, see the tip on 32bit/64bit Rosetta and Classic revisited andCan I download my Mac OS X upgrade?