What happens to my old credit card after a balance transfer?

hi guys

Im looking into doing a balance transfer and was wondering what happens to the original card?

My understanding is that your debt goes to another credit company company, from which you have a certain amount of time with a lowered interest rate to pay it back. But what happens to the original card?

Does it get closed or cancelled? Or is the balance back down to zero again and I could still use it if I wanted to?

Thanks