I think that these thift shops come into two categories in
Britain,
charity shops and
fifty pence shops.
The charity shop seems to be the closest analogy to the thift store: the profits go to the charity who run the shop. Mostly it's women's clothing, but there's a thriving trade in old books (Oxfam seem to do this in particular), kids toys and women's clothing, and there's usually a couple of old vinyl records (usually 60s crooners) and antique computer games (such as Lemmings for the Amiga). There's sometimes some good stuff, but usually not.
Fifty pence shops aren't, any more. Essentially, the idea is that everything in the shop is a fixed price: it used to be 50p, but now it's a pound. These are usually cheap and tacky things, unbranded goods, but have their purposes. They mainly sell washing up liquid and window cleaner, and kids toys and all sorts of stuff. It's all pretty much rubbish, though. And most of it's written in Japanese or Chinese.
Just my 2 pence worth! :)