SMT "Smart Media Tokens" is the general name for any token that you or me will be able to create within Steemit when they release this feature. So we will all have the ability to create our own crytopcurrency tokens that we can use to raise funds (ICO), give out to support projects and communities, or whatever else we need them for.
This is similar to how there are User Issued Assets (UIA) over on the Bitshares exchange that support projects on Steemit now.. Whaleshares, Voiceshare, etc that are given out to people for contributing to community projects or contests, then people can exchange them for upvotes by the person giving out those tokens.
The Smart Media Tokens feature brings that internally to Steemit.
I'm not part of the team creating it, but that is the basic overview. I hope that helps :-)
So glad Steemit is becoming so much more than just the initial "reddit but you get paid" format.