When receiving a loan, you are often required to pledge collateral in the form of an asset (savings account, car, house, real estate). However, with an unsecured business loan, you are being administered the loan simply based on your credit score. Thus, you will need a good credit score (and well-established credit history) to secure this loan.
The downside to an unsecured loan is that you may be charged a higher interest rate. In general, lenders will require some form of collateral, but this is not always the case.