Q: what is powerpc?

It's an older application; Mac OS X 10.7 and newer don't contain the translation code required to run them on Intel Macs. Except by using a newer version of it(if any) or running Mac OS X 10.6.8 or earlier(if needed, use a product such as VirtualBox, Parallels Desktop, or VMWare Fusion with Mac OS X 10.6 Server), you can't.

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The following may help:

https://support.apple.com/en-us/HT201580

http://en.wikipedia.org/wiki/PowerPC

Edited out by dominic23.

Power PC refers to the pre Intel Macs:

http://lowendmac.com/profiles.htm

of these the fastest were the G5s.

These can be bought for a song.