SSL (Secure Socket Layer ) is a security mechanism encorporated in an application , SSL provide the Sekure Transaction of Documents in internetwork environment , it uses cryptography technique for sekure transaction , (i.e. encrypted data passes within networks which can be decrypted using public key ) SSL generally uses in those application where we required a lot of Sekurities , Many payment gateway providers companies use SSL as basic security mechanism.

SSL is security socket layer, it secures the transaction between applications in a network context, those are examples using SSL
http://www.example-code.com/csharp/socket.asp