Secure Sockets Layer (SSL) is a cryptographic protocol designed to secure communications.
In 1996, Netscape developed a protocol for encrypting networks. Not too long has passed and the protocol has become very popular for secure data exchange over the Internet.
SSL methods are integrated into almost all browsers and uses an asymmetric public key cryptosystem developed by RSA. In order for SSL to take effect on your site, you need to install a digital certificate on the server and enable the protocol on port 443 (standard). Port 443 uses the browser abbreviation https (HyperText Transfer Protocol Secure) - an extension of the HTTP protocol to support encryption for increased security.
A digital certificate is a file that identifies users and servers. Typically, a digital certificate is signed and certified by a third party to ensure its validity. The digital certificate can be viewed through any browser that supports this protocol.
It is also possible to create your own self-signed certificate, but in this case, no one can guarantee security, so users' browsers will give errors and warnings, and most likely will not switch to such a site.
SSL will guarantee security when two elements are combined - authentication and encryption. Both of these elements are bound to a specific domain through your server and are checked for security by the browser of the client connecting to the site.
Since 2017, the famous Google began to enforce the use of SSL and stopped trusting sites on http. Since that year, users, going to a site where authorization is possible, will see a mark in their updated Google Chrome "Not secure", thereby encouraging webmasters to switch to https.