Welcome to the webMethods community. A good place to start to learn about the webMethods product line is to visit www.webmethods.com. They provide an overview of all their product offerings. As you determine which products are of interest, you can contact webMethods for additional product details.
Another resource that is quite helpful is Advantage, the customer and partner web site for webMethods products. It provides access to all product documentation, a KnowledgeBase, training information and more. It requires an account to login, which can be requested from the Advantage home page.
And of course, this site provides a lot of material about the various webMethods products. Review the Knowledge Center for articles and white papers that cover various topics.