What is the difference between an electronic and a digital signature?

Different electronic signatures.

Electronic signatures

In South Africa, any mark that is made on an electronic document with the intention to serve as a signature can be considered to be an electronic signature. Although electronic signatures are legal signatures, electronic signatures are not protected with cryptography and is considered to be low trust signatures.

Digital signatures

To protect the Signer and the integrity of the document, digital signatures can be used. Digital Signatures uses Public Key Cryptography to protect the integrity of the document and tie the identity of the signer to the digital signature.
A digital certificate in the name of the signer is embedded into the document at the time of signing.

Advanced Electronic Signatures

Advanced Electronic signatures are a subset of electronic signatures that is governed by the South African ECT Act and is considered to be the highest trust digital signatures.
Only SAAA accredited vendors can issue Advanced Electronic signatures.

For a full discussion see the LAWtrust article: Wet signature vs. Electronic Signature vs. Digital Signature.