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.
Those are the implicit variables -- those that are implicitly included in your JSP page without having to explicitly declare them. The only thing I can come up with for "explicit variables" is any JSP scripting variables explicitly declared within the JSP page. Other than that, I'm not sure what it could mean. bear