With Tag Files, you can invoke reusable content using a custom tag instead of the generic <jsp:include> or <c:import>. You can think of Tag Files as a kind of “tag handler lite”, because they let page developers create custom tags, without having to write a complicated Java tag handler class, but Tag Files are really just glorified includes.
Simplest way to make and use a Tag File
Take an included file (like “Header.jsp”) and rename it with a .tag extension.
Put the tag file (“Header.tag”) in a directory named “tags” inside the “WEB-INF” directory.
Put a taglib directive (with a tagdir attribute) in the JSP, and invoke the tag.