Use for questions referring specifically to versions of OS X 10.5, Leopard. Non-version-specific questions related to OS X should be tagged with [osx]. Questions about Mac hardware should be tagged with [mac]. Questions about running OS X on non-Apple hardware are generally considered off-topic.
OS X (pronounced OS ten; "X" is a Roman numeral), version 10.5, codenamed Leopard, is the 6th major release of Apple's Mac operating system. It was released on October 26th, 2007. It is a Unix-based graphical interface operating system.
Leopard is a 32 bit OS that supports PowerPC and Intel processors (although, an Intel processor is required for some applications and actions). It is the last version of OS X that runs on PowerPC-based Macs.
The retail version was a universal release, running on both PowerPC and Intel processors, while the install version that shipped with Intel-based Macs contained only Intel binaries. Leopard included Rosetta (software that allowed many PowerPC applications to run on Intel-based Macs without modification).