A secured line of credit is a revolving source of funds that’s backed by collateral, like a piece of equipment or a building. Since you're using valuable assets to guarantee your line of credit, you may qualify for a higher credit limit at a lower interest rate.
An unsecured line of credit is a revolving source of funds that isn't backed by collateral. Since you're not using valuable assets to guarantee your line of credit, your interest rate may be higher and your credit limit may be lower.