Declarations
It is similar to variable declarations in Java. Declarations are used to declare variables for subsequent use in expressions or scriptlets. To add a declaration, you must use the sequences to enclose your declarations.
Expressions:
A JSP expression is used to insert the value of a scripting language expression, converted into a string, into the data stream returned to the client, by the web server.
Expressions are defined between <% = and %> tags.