Sounds like a cloud. Meaning its a hard drive that is not hooked up to your ps3 so you don't have to worry about losing anything if your ps3 go's to doodoo also it can save alot of needed room on your ps3 hard drive ( I believe this is what it is)
And I believe you do get to keep most of the stuff sbc, this is why they give things for free every tuesday and some of the stuff will end up not being free anymore, they do that so somebody doesn't just pay for one month and downloads everything they have ever made free and then cancels
if your subscription runs out you can't use free games anymore. discounted games you got you keep though.