An SSL certificate is a digital certificate that authenticates a website's identity and enables an encrypted connection. SSL stands for Secure Sockets Layer, a security protocol that creates an encrypted link between a web server and a web browser.
Companies and organizations need to add SSL certificates to their websites to secure online transactions and keep customer information private and secure.
In short: SSL keeps internet connections secure and prevents criminals from reading or modifying information transferred between two systems. When you see a padlock icon next to the URL in the address bar, that means SSL protects the website you are visiting.
Since its inception about 25 years ago, there have been several versions of SSL protocol, all of which at some point ran into security troubles. A revamped and renamed version followed — TLS (Transport Layer Security), which is still in use today. However, the initials SSL stuck, so the new version of the protocol is still usually called by the old name.