The ARP protocol can also be used to find the IP address of a device when only knowing its MAC address.
When ARP is utilised to find an IP address, it is called RARP for "reverse ARP".
This is a common situation in the so-called "bootstrapping", or starting from zero. In such cases a device X may not know its own IP address, but know its MAC address, since it is embedded in the hardware. But who knows X's IP address if not X itself?
The answer is a RARP server. The RARP server listens for RARP broadcasts and responds to them with the appropriate IP address.
The process for reverse address resolution avails itself of the same ARP protocol and the terminology remains the same, except that the source and the destination may now be the exact same device.