It is the hashtag you use to get pal tokens.
They have an interface you can use that may give additional benefits, it adds the hashtag, at least.
If you go to steempeak.com, find the tribes link, there is a complete list, and one click access to the tribes.
Tribes consolidate content on certain topics, mostly.
Stem does science, sports does sports, palnet and neoxian are general.

Maybe the tokens moon, maybe they do nothing.
They are an experiment in income redistribution.