It's very simple. All you do is make one affordable monthly payment to a qualified legal professional, who in turn distributes the payments according to the amounts previously agreed by your creditors in an IVA proposal.
You do this every month, for 60 months, and at the end of the term any debt balances you still owe are written off. You don't have to deal with nasty creditors any more, and all the hard work is done for you. And since an IVA is a legally binding agreement, your creditors can't back out or change the terms after they agree to them.
An IVA is often considered to be a great option for people who find themselves in debt.