Autofill is a feature found in web browsers and applications that automatically fills in forms with previously saved information. This can include details like names, addresses, email addresses, and credit card numbers. By using autofill, users can save time and reduce the chance of errors when entering repetitive information. When a user starts typing in a form field, the autofill feature suggests relevant entries based on their past inputs. This functionality enhances user experience by streamlining the process of completing online forms, making it quicker and more efficient to navigate websites and applications.