We use Comodo to secure our customer transactions. Our customer can be assured that it is safe to do business with us as all sensitive information is encrypted and will remain private.
On the surface it is fairly simple with a request being sent to a web server for a secure transaction. The server sends out its public key, which is generated on the spot. The client (your Web Browser) receives this key and encrypts all messages with it. The server and only the server can decrypt the messages and it will then respond with a message encrypted with the server's private key. The client then uses the public key to decode the server's transmission.
In addition the SSL process checks to make sure the server the client is transmitting to is who it's supposed to be.
Contrary to popular opinion, Website's that employ SSL, like ours, offer you more protection than most offline merchants that accept credit cards.