More information on the details of the Wolfram Workbench may be found in this help section which focuses on the Mathematica specific features. However, the rest of the Workbench help system may also be useful.
Information about what the Wolfram Workbench is and how it fits with other Wolfram technologies can be found at http://www.wolfram.com/products/workbench. In addition, some screencasts are available at http://www.wolfram.com/products/workbench/screencasts. These give live demonstrations of how the Workbench can be used.