Object is very loosely defined in maya. What you think of object type is almost always NOT what maya is actually selecting. So 99% of the time you either select a transform or a joint. Because everything maya selects IS a category of transform. And thats basically just joint and transform.
You can querry it with
ls -sl -showType
which gives a alternating list of object name and its type. Now you may notice thet mayas actually quite booring as it says transform most of the time. Tahts because its correct.
now IF you want to force your viewpoint on maya it would be closer to whet humans tend to think of as objects youd do:
ls -sl -dag -shapes -showType
But even that is a sometimes slightly unsatisfactory because maya doesn't do selection the way people seem to intuitively think either. You can convolve beyond this if you wish but remember the further you go the less the answer is about whats really there. Lying to oneself is always counter productive.