A NAM is a Network Access Module. It's also known as a Network Jack or Network Outlet. It's usually located low on a wall, is putty colored, with RJ-45 type ethernet ports. Older NAMs have telephone ports and ethernet ports. Many rooms have two or more NAMs.
To prepare for upcoming Voice Over IP (VOIP) telephones only networking ports will be installed. When VOIP phones arrive, it is expected the phone will plug into a network port and also act like a switch, providing a network port for a desktop computer. Until then, current phones will be cabled through a network port.