https://www.aetna.com/individuals-famil ... count.html
You put some of your income into the account and it isn't taxed. You can then spend it on stuff like prescription glasses and dental work. I'm in the 25% bracket, so add state income tax and the saving is more like 1/3.
The card I have for my FSA works like a debit/credit card. Too much hassle. I've decided to only use my FSA for high dollar stuff like dental work that I can plan in advance. Then, after it is all done, I submit the paper work and they deposit the money in one of my accounts. But yes, you can use it like any other plastic as long as you only buy certain items.