What happens when debts from credit cards or past due rent go into collections? How does repayment of it work?

a credit card company hired a law firm to collect my past due amount. I'm sure i'll have other things going into collections as well, including past due rent. I lost my job and cant afford to pay all of these people what they want and they wont accept what I can give them. So I'm curious about what happens when past due amounts go into collections.