An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It serves two main functions: host or network interface identification and location addressing. Other options, while related to networking, do not serve as unique identifiers for devices on a network. MAC address is unique to the network card but is not assigned by the user or network administrator. Network name is a human-readable label for a network, not an individual device. Subnet mask is used to divide the network and the host portion of an IP address.