An SSL certificate is a file installed on the web server that a web site
is running on. This file is composed of two segments. The first is the
public key, which encrypts data. The second is the private key, which
decrypts data. When a client, such as a web browser, connects to an SSL
secured server a unique session is created using these two keys. All
data transmitted during this session is protected, and cannot be
decrypted by any party other than that specific client and the server.