Mentally, moving the money into different envelopes keeps you from spending money you don't have. Behind the scenes, I think they only use one bank account with one account number, but it helps you mentally keep track of where things should be.

You can specify daily transfers to slowly fill up an emergency fund or vacation. The beauty is when your car breaks down, you might have a repair fund that you can deduct from and you don't see your main balance drop.

But it's all just lipstick on a bank. When I used them, I think it was Bancorp, but they moved to a spanish bank when I hopped off.