In Autodesk Navisworks, you can create and use sets of like objects. This makes it easier to review and analyze your model.
Selection sets are static groups of items, and are useful for saving a group of objects that you want to regularly perform some action on, such as hiding them, changing transparency and so on. They simply store a group of items for later retrieval. There is no intelligence behind this set - if the model changes at all, the same items are selected (assuming they are still available in the model) when recalling the selection set.
Search sets are dynamic groups of items, and work in a similar way to selection sets, except that they save search criteria instead of the results of a selection, so that you can re-run the search at a later date as and when the model changes. Search sets are much more powerful and can save you time, especially if your CAD files are continuing to be updated and revised. It is also possible to export search sets, and share them with other users.