Can someone explain a 0% APR credit card?

The teaser rate is just to get you hooked. After that, it's just like any other credit card: a bad deal if you're not paying the balance in full every month. I really mean this kindly, but I think your main issue is not the interest rate on your card, but your spending choices. It sounds like you've let your card balance grow with the limit, and now you're pretty much maxed out. It's wonderful that you've never been late on minimum payments, but honestly, you're one missed payment away from falling off a cliff. What you need to do is back away from the edge.

If you don't already have a debit card attached to a checking account, I'd suggest you get one of those. Be sure to decline overdraft protection on that account. That's effectively the same as a 0% interest rate card on what you buy, forever.

Do whatever it takes to pay at least $200 a month on the credit card. It might mean no new clothes at all, or that you bike instead of driving, or that you don't give buy any gifts for Christmas (write a heartfelt letter to each of your friends and relatives, that will be worth a lot more than anything that could be bought in a store on online). I had to go on extreme savings measures twice in my life, and it's sort of an adventure, once you get into it.

Stop using the credit card completely, even as the balance decreases, because everything you buy is basically getting charged 19% interest a year, for many years.

Those are just limited time teasers, reading the fine print you may find the interest rate of one of those offers is higher than what you are paying now.

I'm ignorant as to whether you can just transfer balances from your existing card to a 0% offer to save on interest for a few months, I rather doubt it, you would probably have to get a higher interest cash advance card to pay off the old card, you could calculate if the months of no interest would still leave you ahead by the time you paid down that cash advance balance.

You pay no interest on balance ...but probably only first 6 months or something like that and after that you are screwed .Or there is some other small print .

No annual percentage rate. You don't pay insterest on your balance.

Maybe it is good