To get data off the Web with LWP, you really only need to know about LWP::UserAgent objects and HTTP::Response objects (although a rudimentary knowledge of the URI class and the HTTP::Cookies class can help too). But behind the scenes, there are dozens and dozens of classes that you generally don't need to know about, but that are still busily doing their work. Most of them are documented in the LWP manual pages, and you may see them mentioned in the documentation for the modules about which you do need to know. For completeness, they are listed in Appendix A, "LWP Modules".