An advanced electronic signature (AES) is a more sophisticated and secure form of the electronic signature.
It is a digital signature that is created with public key cryptography (PKI) and inserted into the code of the electronic document. It contains an electronic certificate issued by an official certification authority under strict requirements.
The eIDAS regulation requires AES to be:
Uniquely linked to the signatory
Capable of identifying the signatory
Created using signature creation data that the signatory can use under their sole control
Linked to the signed data in such a way that any subsequent change in the data is detectable