generally it is a Poly Resin that comes in two parts that you have to mix and pour on.
It is highly toxic and the fumes will gag you so make sure you do it outdoors and there is NO wind/dust in the air...or indoors with an extremely well ventilated area!
something like this, but I know that stores like Hobby Lobby and Michaels also sell a more user friendly one!
http://liquidglasscoating.com/