What's the difference between simple, advanced and qualified signatures?

These three levels come from the EU eIDAS regulation:

• Simple signature (SES): the fastest, ideal for everyday low-risk documents (quotes, purchase orders, internal attestations).
• Advanced signature (AES): adds stronger signer identity verification (e.g. an SMS code) and a firm link between the signer and the document. Recommended for commercial, HR or lease contracts.
• Qualified signature (QES): the highest level, the legal equivalent of a handwritten signature, with identity verification by a qualified provider. Required for certain sensitive deeds.

In practice, the advanced signature covers the vast majority of business needs. You choose the level when preparing the envelope.