You could be purchasing a home from a bank, which then holds the lien on your home until you repay your loan. A car on which you are making payments, is another example of a secured loan. Unsecured debt is any debt that has no collateral backing the loan. Credit card debt is a prime example. Signature loans are another.
Unsecured creditors can usually expect to get little if anything in a bankruptcy.
This information is general and should not substitute for the counsel of a licensed attorney.