You have connected a Switch or Router 48 ports to a network, how the device can know which device on the network on which port in the device?

arp, cdp, mac-add-table. That is enough to explain.

if it is Juniper it will learn the neighbout details through LLDP and CDP in case of CISCO. On the same case for interface details it will verify the MAC table if it is L2 or ARP entries if it is L3.

Using CDP and MAC Learning

As the traffic starts flowing through the switch, it starts building an ARP table, which binds the MAC address to the IP address.

Thus a network engineer can build down to finding which device is connected to which port. The MAC's indentified can further be used if port security needs to be implemented.