In the context of bail, a personal bond is a written promise by the accused, guaranteeing their appearance in court and compliance with bail conditions. A surety bond, on the other hand, involves a third party, the surety, who guarantees the accused's appearance and compliance, often with a financial guarantee (like collateral)

A personal bond is a promise by the accused to appear in court without needing a guarantor.
A surety bond requires another person to guarantee the accused's appearance and take responsibility.