Geotools focuses on being a Java code library, not an application. The library provides methods to manipulate geospatial data. While the library facilitates the creation of maps, by default, Geotools provides almost no Graphical User Interface (GUI) functionality since the library can be used for servers on the World Wide Web, as in Geoserver, or for desktop applications, for example UDig. The LGPL license is flexible enough for Geotools to be used to create both open source and commercial applications.
This page, and the sections below, attempt to provide documentation for new users. Unfortunately, this older documentation is a mess, mixing code examples from various different releases. The Geotools team is working on a Users' Manual which will present things more systematically.
The Geotools User Guide (in progress)
The user guide is a work in progress which will be the primary documentation going forward.