Supressed/Lightweight/Resolved/Unsupressed are really not the same. In context of an assembly a component can be: Supressed- it, and all its children mates,in-context references, ect. completely discounted from the assembly Unsupressed but lightweight-above items visible and updated based upon the latest time the component was in a resolved state. Used when dealing with a larger assembly to reduce overhead, but may not be 100% accurate as lightweight sub-assemblies/parts may have changed since their last resolved state. Unsupressed and resolved-the most accurate condition of an assembly. The component/sub-assembly and associated references are updated to its actual current state.
Its really a speed issue. Working on a 5000 piece assembly in a fully resolved state will be much slower, but much more accurate than working on the same assembly in lightweight mode. Thankfully, you can selectively resolve only those parts/subs necessary to ensure accuracy in the area of the assembly that you are currently working. There is no lightweight state of a mate, its either there... or not.