Smart Components is functionality that can save you a lot of time; the more standard parts or assemblies with associated part-level features that you insert into your assemblies, the more time it can save you. Like anything else of much automation value, it does require some setup, but the setup is a one-time thing.
Smart Components are parts or assemblies that you can place into an upper-level assembly and that carry with them mounting features and hardware (cut-outs, mounting holes, and even fasteners). Smart Components are configurable and can automatically size themselves on cylindrical parts.
A Smart Component can comprise several elements:
A single part or an assembly that may use size configurations
A configurable library feature that usually serves as mounting holes or a viewing window for the Smart Component
Associated hardware that may also be driven by size configurations
A training assembly that is used to define the Smart Component
Some minor limitations exist, as you might expect:
A Smart Component part cannot have references that are external to the Smart Component group of which it is a member
When placed in the assembly, the associated library feature can only affect one component
The associated library feature is limited to one of several feature types:
Extruded or revolved ...