Debtors prisons were used to incarcerate people who borrowed money and failed to pay it back. Since being in prison prevented most people from earning money to pay back their debts, many debtors spent a great deal of time in prison. Often the families would gather up the necessary funds to get the debtor out of prison. In some cases debtors were forced to work as indentured servants until the debt was repaid.
In the US bankruptcy law has made it unlikely that debtors will go to prison. Still there are some situations where you can be thrown in jail for not paying your debts. Money owed to the IRS is not canceled by bankruptcy ruling. Debtors are still obligated to pay taxes regardless of their bankruptcy status.
While debtors prisons were the source of many human injustices, they did make people take debt more seriously. When bankruptcy was not an option borrowers had serious consequences to face if they were not able to pay back a loan. This would have prevented people from taking unnecessary risks with borrowed money. On one hand that might have slowed economic growth, but it also encouraged people to act in a more prudent manner.