A Tag Library is a set of useful tags packaged and distributed together which help web application developers accomplish related tasks
There are five tag libraries available with Struts 1.1.
Struts-html : These tags useful for creating dynamic HTML user interfaces and including input forms.
Struts-bean : These tags useful for defining new Beans, in any scope, from a variety of possible sources.
Struts-logic : These tags useful for manipulating presentation logic without the use of scriptlets.
Struts-nested : These tags useful for extending the current Struts tags to allow for nesting. This library provides the ability to define a nested object model, represent, and also manage that model.
Struts-template : These tags useful for creating dynamic JSP templates for pages that share a common format.