Found in the feature tree once an assembly is opened

View

Saved state of part visibility. Use view reps to create views for drawings.

Level of Detail

Saved state of component suppression Suppressed parts don’t load into memory when you have that LoD open Almost required when working with massive assemblies due to performance/stability reasons

For Drawing Views

Always use view reps to create partial views of an assembly for use in drawings. This is because Level of Detail views will automatically include any extra components you introduce into that assembly. View reps do not!: Parts added after the view was last saved will not appear in the assembly for that view rep.