Java Tutorial - Java Script :
A JSP page consists of three kinds of elements, each with its own special markup tag that’s similar to HTML:
Scriptlets—Java statements executed when the page is loaded. Each of these statements is surrounded by <% and %> tags.
Expressions—Java expressions that are evaluated, producing output displayed on the page. These are surrounded by <%= and %> tags.
Declarations—Statements to create instance variables and handle other setup tasks required in the presentation of the page. These are surrounded by <%! and %> tags.
