Basically its flavoured smoke, such as double apple and so on. Its formed like a Bong, u smoke through a pipe but you get smoke but its flavoured.
I smoke that all the time, im normally down shisha bars such as edgeware and so on.
They are bare flavours:
Banana
Mango
Grape
Plum
Lemon
Mint
The best is double apple smoked actually from a apple u shud try that.