Ok you get low and high modulas sealant, now i know high is for bathroom and low is for frames but what does it mean ?

Cliff

Modulas of elasticity maybe?

High for bathrooms as the bathroom sealant needs to flex when the bath moves ( as it could if plastic and filled with water). Low for windows that dont move but need to be a bit more secure??

It actually sounds the wrong way round but low mod silicone is better quality than high mod silicone and if its to be used in a bathroom always ensure you use a sealant with anti fungal ingredients - otherwise it will go black and mouldy within a couple of months.
look on the draper site they have some info

http://www.drapertools.com/draper/Templates/draper/MainScreen.asp