Python is a programming environment. Poser happens to support this language to do some neat things. You will find some scripts sprinkled around if you look. I haven't really looked at the Merchant section, so there may be more than I know.

As for version support, if I remember correctly, Python support began with Pro Pack for v4. I may be off base with that though. Once you get P6 though, it is definitely there.

As far as tutorials, there aren't many, if any. I have yet to find one, and I have been looking. One good thing you can do though, is go to the Python site at Python.org. There is a ton of info on the language there. Hopefully once I have had the chance to play with the scripting environment, I can make a tut or two.