Answer Description
Port Security also known as MAC Filtering is used to restrict which devices can physically connect to the network. This is done by whitelisting which MAC addresses (the physical address of a Networking Interface Card (NIC) are permitted on the network. It is most commonly done where a network port like an RJ-45 is publicly accessible like in an office waiting area.
Wikipedia
In computer networking, MAC Filtering refers to a security access control method whereby the MAC address assigned to each network card is used to determine access to the network MAC addresses are uniquely assigned to each card, so using MAC filtering on a network permits and denies network access to specific devices through the use of blacklists and whitelists While the restriction of network access through the use of lists is straightforward, an individual person is not identified by a MAC address, rather a device only, so an authorized person will need to have a whitelist entry for each device that he or she would use to access the network
MAC_filtering - Wikipedia, the free encyclopedia