SSL is 'Secure Sockets Layer' - a technology developed a few years ago, to solve two major problems, regarding the transfer of sensitive data over the internet to the final customer, SSL offers two features for addressing the weaknesses described above.
Encryption - This means adding layers to data in transit between client and server; translating the intercepted data into something unintelligible for any third party (without the application of huge mathematical processes). SSL offers various levels of encryption, from '40-bit '(US export Grade) and up to 128-bit (US Domestic Grade). In essence, the more bits, the stronger the encryption.
Authentication - This is the requirement for a truly secure connection between the client and the server, both parties having to ensure the identity of the other. There are ways to mathematically prove the identity of the remote party at the end of a secure connection.
SSL is a 'transport level' - in which other Internet protocols can be transported in an encrypted way. The most commonly used method is 'HTTP over SSL'. When HTTP travels via SSL, this is indicated by a different URL starting with https: // instead of http: //
To date, no significant weaknesses have been found in the SSL protocol and it is widely accepted as a standard for data transmission security. This is due in part to the network established by authoritative servers that distribute SSL certificates.