In Computer Networking, and in particular to WiFi-networks, we learn that a "mobile node" (i.e. any mobile unit that can access a router through WiFi) has a permanent IP-address (the "home address"), and an intermediate address ("Care-of-address") when visiting foreign networks, which gets assigned whenever said mobile node associates with a foreign network/router.
"A mobile node is given a long-term IP address on a home network. This home address is administered in the same way as a "permanent" IP address is provided to a stationary host. When away from its home network, a "care-of address" is associated with the mobile node and reflects the mobile node's current point of attachment. The mobile node uses its home address as the source address of all IP datagrams that it sends, except where otherwise described in this document for datagrams sent for certain mobility management functions."
I'm having problems understanding the concept of the home address, and how/when this is assigned to the mobile node. What defines the "home network" and "home address" that the protocol refers to here?