A certified check or certified cheque is a form of check for which the bank verifies that sufficient funds exist in the account to cover the check, and so certifies, at the time the check is written. Those funds are then set aside in the bank's internal account until the check is cashed or returned by the payee. Thus, a certified check cannot "bounce".
In some countries, e.g. Germany, it is illegal for a regular bank to certify checks[1]. This regulation is supposed to prevent certified checks from becoming a universal substitute for cash, which is considered the only legal tender. The Deutsche Bundesbank (Federal Bank) is the only financial institution authorized to issue certified checks.