They have some of their own, also use AWS and others too.

AWS is just used for storage, because it's cheaper than Apple maintaining it, itself. Apple do have storage-datacenter at their campus at least (I've walked around one, it's many many racks of SSD's) but almost all the public stuff is on AWS (wrapped up in encryption) AFAIK.

Apple datacenters are mainly compute, other than the storage you need to run the compute efficiently.