I found this drain in my basement in the middle of a raised rectangle of concrete. Its supposed to be for a shower the previous owner installed. I have never seen this drain type. Looking for answers for what kind of drain it is and why it would have been installed.
That is a bone stock "bell-trap" floor drain.
They are illegal for interior use under the IPC (at least) since the trap weir depth is perhaps 1/2 an inch or so; well below the minimum 2" weir depth required, in any case - though in fact the exclusion is for ANY bell-trap, not specific to the depth of the trap, but in this case that is typically about what you'll have. 1002.3, (Prohibited traps) item number 2 (Bell traps)
They can be used for exterior or garage drains (not connected to the sewer) only, as I recall. I just removed one and "de-trapped" another (cut the inner ring seal so it just acts as a collector) and installed an actual P trap (adjusted to 4" weir depth) on its line. Fun chopping holes in concrete, yes indeed.
It probably was installed for a shower. They look like a perfectly reasonable, easy to clean option and the large box store will happily sell them without telling you that they are illegal for interior applications.