Assemblies are a series of Components/Sub-Assemblies that make up a higher level Assembly
Every Assembly begins with a base Component. This component is the primary component such as the Chassis to a vehicle
The first component is often the largest, or at least the one that exhibits the least movement and the rest of the components are attached to
Assemblies require multiple Components. Once the Assembly has been created, Components may be inserted:
The relationship between Components are considered Mates
Components are either Fixed or Floating
Once Assemblies become sufficiently complicated, you may benefit from Isolating the two Components that you're aiming to Mate
Components may also be Hidden/Shown by using the Tab/Shift+Tab while hovering over the Component