SSL stands for Secure Socket Layer. It is an mechanism to transfer information securely across the Internet. SSL will enable your customer's browser to connect to your web site and transparently negotiate a secure communication channel. Once this connection has been made, information, like credit card numbers, can be exchanged securely. 

Please note that SSL does not include software to process credit card transactions. Although you can securely receive credit card information through SSL, actual processing of the credit card will require a "Merchant Account" from an accredited financial institution.