SSL fingerprinting is a way to identify if a website is secure or not. It uses a mathematical formula to create a unique identifier, or 'fingerprint' which is like a digital signature for the website. When you visit a website, your computer will calculate the fingerprint of the site and compare it to the fingerprint it was expecting. If the fingerprints match, then the website is secure, and you can safely visit the site. If the fingerprints don't match, then the website might not be secure and you should not visit the website.