Compost tea is made by putting a bunch of compost inside a bucket of water and bubbling air thru it as its warmed. This is to get the beneficial bacteria and fungi excited and alive inside the liquid. The liquid is then cooled and used to water your plant.
The stuff you bought are the bacteria and fungi and prob some extra food for them to add to your compost tea to supposedly make it more potient.
IMO its a rip off. But, in my situation, i compost all of my yard waste so every year i end up with a couple of tons of it and i can make my own tea. I also use soil. I dont know if you would want to use compost tea in a hydro set up.