Projects can directly contain many machine tools. They are shown under the Machine Tools branch in the Explorer.
A machine tool is an interactive 3D model of an actual machine tool. Unlike the other entities in the Explorer, machine tools cannot be created in PowerMill, instead they have to be imported. The expectation is that you import a machine tool that is the same as the actual machine tool in your tool room.
This enables you to accurately visualise the machine tool whilst simulating toolpaths or NC programs, as well as checking for collisions.