SSL (also know as Secure Socket Layer) is a protocol which ensures secure transaction between the client web browser and the server. SSL was developed by Netscape. The protocol actually uses a Certificate Authority (CA) to verify both or one side of the transactions.
If an SSL certificate is installed on the site, the browser requests a secured page from the server (which is done via
https://). Once the request is received by the server, it sends the public key with its certificate. After this, the browser checks if the certificate was issued by a trusted party (which is done through CA) and if the certificate is valid. Then, the public key is used by the browser to establish a secured connection with the server and the http data is encrypted.
I have tried to explain the process in simple terms and I hope this helps
