s referred to as a declaration block.
it can also be written in xml syntax...for example
<jsp:declaration>
String user_name = new String();
</jsp:declaration
the following is a comment
the following is an expression
Say for example, you have a string and it contains a user's name "John Smith" and you want to print it...you can write
<%= name %> instead or typing <% out.println( name ); %>
Greetings
Daniel