WTP platform server
As seen above, there appear to be two JBoss categories. The first is contributed by WTP, and is a generic adapter that is not upkept very well. For this reason, JBoss Tools provides updated and supported adapters of our own. There is one for each of JBoss 3.2, 4.0, and 4.2. You'll also note a deploy-only runtime type. This type provides no classpath for WTP projects. It is used solely by it's server type for the purpose of setting up a deploy directory for users who don't wish to make use of starting, stopping, or debugging their projects inside eclipse.
As shown above, all you need to do to create the runtime is to name it, browse to it's install directory, select a Java Runtime Environment, and select which configuration you want. As you browse to a valid installation folder, the list of configurations will update allowing you to select the configuration of your choice.
http://docs.jboss.org/tools/2.0.0.GA/as/en/html/runtimes_servers.html
WTP Projects
WTP provides what are called "faceted" projects. Their most popular of these projects are their J2EE projects, such as their Dynamic Web Project, their EJB Project, or their EAR project. Web projects of JBoss Tools are Stuts, JSF and Seam projects.
The idea behind faceted projects is that each project can accept units of functionality, or facets, which can be added or removed by the user. Some examples of these facets are adding a webdoclet facet to a web project, or an ejbdoclet to an EJB Project.
Most often, these "facets" either add to the project's classpath, enable a builder, or watch the project in some other fashion.
WTP projects have undergone some criticism as being over-engineered or too restrictive in their design. WTP projects are set up in a tree-relationship to each other, where one project can be a child of another. For example, an EAR project may have a Web Project child, an EJB project child, or other types.
The benefit of this is that the structure of your projects is then known, and packaging it up *should* be trivial. However, if your project is non-standard, or you feel too confined by such rigid structural requirements, you can still choose to package your project using the Archives plugin.