Import - Layers tab

The Layers tab can be found at the bottom of the .Obj Import dialog...

...these options determine whether Cinema 4D (R10.1 or later only) "Layers" are created for various tags on the new mesh, to help organization. Note that the Material, Group and Region Tag settings also affect the related Polygon Selection Tags (all Polygon Selection Tags used as Group selections would be in the "Group" layer, etc.).

Due to the extensive use of Polygon Selection Tags (separate tags are used for each Group, each Region and each Texture/Material on the mesh), the Object Manager display can get quite cluttered. Having Layers created for them allows you to show/hide those tags, to help manage that clutter.