SimMechanics includes both First-Generation and Second-Generation technologies. Second-Generation technology offers a redesigned block diagram language focused on local component definitions to support reusability and library development. It also offers more advanced 3D visualization and animation capabilities that are tightly connected to the block diagram representation. You have the option to create and simulate a mechanical model using First- or Second-Generation technology.
For more information on the difference between these two technologies, see the SimMechanics documentation and Release Notes.