This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
basically the "S" of HTTPS adds security and optional authentication mechanisms to the HTTP protocol if needed. The security mechanisms are based on certificates but perhaps you want to take a look into Wikipedia to get more information.