If the lock is closed or the key is solid, you are on a secure site. If the lock is open or the key is broken, the site you are visiting is not secure. SSL is an encryption technology called Secure Sockets Layer. SSL provides secure communications over the Internet by verifying that the server to which you are connected is the one it claims to be. It also encrypts all transactions between the parties communicating.
Encryption is the way in which information is scrambled when it is sent over the Internet.
Your data is made indecipherable to any other party when encryption is used. The strongest form of encryption available over the Internet today is 128-bit. You can test your browser to see if it's 128-bit enabled. A cookie is a file sent from a website to a computer that is logged on to the site. This file lets the site recognize if the computer has been there before and what security requirements and browser preferences the computer requires.