PowerPC, POWER, and Power	What is it?
Why use it?	What hardware can run it?

It's just marketing. "PowerPC" was the original name of the architecture developed by IBM, Motorola, and Apple. IBM invented the "POWER" brand to distinguish its server PowerPC processors from embedded and desktop PowerPC processors.

When Power.org was formed, IBM decided that "PowerPC" sounded too much like "personal computer", a market PowerPC vendors were abondoning to x86 processors. So in a move sure to reduce confusion, they renamed the PowerPC brand to "Power Architecture Technology", abbreviated to "Power" (with lower-case letters). (See also this forum post for a marketing spin on it.) Try googling for "power" and draw your own conclusions about the wisdom of this decision.

Technology people like us ignore the silliness and call it by its original, unambiguous name: PowerPC.

PowerPC Linux is the Linux kernel running on a PowerPC processor. Linux and PowerPC processors can be found all over the computing industry.

PowerPC is a well-established architecture that's been used in high-end and embedded production systems since 1994. Linux is the fastest-growing operating system and supports a wide range of hardware, large and small. In fact one of the advantages of PPC Linux is its binary compatibility: a program built for a high-end server will work equally well on your desktop.

Because Power Macintosh contain PowerPC chips, many PPC Linux users were originally Mac users. One of Linux's advantages is that it supports old and slow machines quite well, meaning a Mac that is unable to run Mac OS X can still be useful as a server or even a workstation. Along similar lines, some companies have found they can convert old RS/6000 and pSeries to run Linux and much more current Linux software, such as virus- and spam-filters.

In recent years, many companies have been purchasing new PowerPC-based systems explicitly to run Linux. Linux is used in a large number of High Performance Computing (HPC) systems, and PowerPC is a very scalable architecture, capable of supporting more than 32 processors and absurd amounts of memory in a single server. In contrast, x86-based systems need to use some performance-impacting tricks to use so many processors and so much memory.

There is also a long list of reasons why embedded systems vendors like PowerPC Linux.

PPC Linux runs on a wide range of hardware, from embedded systems like the TiVo Series 1 to Power Macintosh desktops all the way up to high-end pSeries servers. Processors supported include the embedded families: 405, 440, 850, 860, 8500; the desktop families: 603, 604, 750 (G3), 74xx (G4), 970 (G5); and the server families: POWER3, RS64, POWER4, POWER5.