The name mahiyya comes from the Arabic ’má hiyya’:
This is the question “what is it?” where “it” is anything in the universe, visible and invisible, in the empirical or in the imaginal world.
In other words it is the question “what is its essence?” “what is its reality?” (quiddity).
So it is about the investigation into everything else than God – Allah:
The creation, the cosmos, macro- as well as micro ~.
To know God – Allah through His signs, His names, His creation (al-wujúd ), His Sunna, not the least through ourselves (our souls), and to serve Him is the highest, most noble endeavour; – we can never know His essence and we don’t need to.
”A thing’s “reality” (haqîqa), is its “whatness” or “quiddity” (mâhiyya). This is determined not by our definitions, but by God’s knowledge, because He knows the thing always and forever, whether or not it exists in the cosmos.” Muhyiddin Ibn `Arabi