It is the RAM that your iPod Touch has to basically run your apps. If the RAM is too low then it is more likely that apps are going to crash. Depending on which version of the iPod Touch you have... will depend on how much RAM it has and so on. I think the 3rd Gen iPod Touch has 256mb of RAM... and i think 128mb for the 2nd and 1st generation. Someone correct me if I'm wrong. As for freeing it... Apple told app devs that made apps like that to pull that function. I've kept my apps from updates so that I can keep it in case it's necessary. So currently can't think of a way to free it.... I know there is a way to do it through SBSettings when it is jailbroken though.