A switch is an interconnection device used to form a local area network (LAN) and whose Technical characteristics follow the Ethernet standard by connecting several devices in a network.
A Power Line Communication (PLC) is used in communication networks to transmit an internet connection through the electrical network in order to expand the Wi-Fi network and the Ethernet connection.
A WiFi repeater is used to extend the coverage of a home network economically. These capture an existing Wi-Fi signal and extend it with their antennas so that it reaches even further, this being the same signal as the existing one. That is, it acts so that the WiFi signal reaches areas where it does not reach its coverage from the router.