Join coinstarter.com and all will become clear. Read the site, take it in, understand what it's about.
Also, liquid.com isn't the only place that trades Stac - Etherflyer is probably a better option, albeit more expensive (but still insanely cheap). There are more exchanges - you just have to find them.
https://www.etherflyer.com/trade.html?pairs=STAC-ETH
Coinstarter is a crypto-crowdfunding platform. Basically projects come there to list and to get more reach (there are thousands of us registered on coinstarter, or at least there was at the beginning). Those that want to promote their coins leave a little bit of their ICO coins for us Stac holders to collect. We do so by swapping our Stac to collect x amount of x ICO coins every 5 hours (depending how many ICOs agreed to do so - I expect there are bonuses for those that do (although I'm not sure)) Right now I'm currently collecting 4 ICO coins 4-5 times per day.
I don't know how to explain it better than that, sorry.