Secure Sockets Layer (SSL) and Transport Layer Security (TLS) are both very important to the security of the internet. They are the protocols that encrypt any secure connection between you and the server.
When you connect to the server, a “handshaking” process begins. The first step is that the server sends you its identity certificate and public key, then it asks for the same from the client. The client then responds with its public key and verifies the server’s identity certificate with the certificate authority that created it. Once this has been successfully completed, the connection can now be encrypted.
If those steps are not completed, the client can not trust the server and closes the connection.