How SSL Works:
1) The user requests a website using https eg: https://www.yoursite.com , the server receives the request and sends a certificate and public key to the web browser.
2)The browser checks if the certificate is trusted by checking it with the trusted certificate authorities it already has. The browser by default has some trusted certificate authorities. You can view it in the settings of your browser.
3)If the certificate is verified by the web browser, then it sends the requests to the web server by encrypting the requests using the public key issued by the web server. The web server in turn decrypts it using the private key it holds.
Thus a secured connection is established between the web browser and web server.