PC hardware--CPU & Motherboard & RAM/Wireless External Hard disk drive.
The external hard disk drive can also be a Wireless device?.
I had seen a few implementations where the external drive has a built-in radio, but had not been very successful. I understand the stability of the connection is not very stable.
What is usually the way to do it is attaching the drive to a router or AP via USB, and have it providing the file services for the wireless devices. My personal experience is leaving it to the router/AP is not dependable, and rather have a NAS wired to the network providing the file services to wired and wireless clients with an AP for the wireless devices access to the network. It's a bit more convoluted, but works for me.