What is an sfp slot on a switch?

FL SFP SX - Media module - 2891754 sfp slot Perle USA Store: S-1000-SFP Media Converter 1000Base-T, SFP Slot VPN: 05050184 sfp slot switch SFP ports enable Gigabit switches to connect to a wide variety of fiber and Ethernet cables in order to extend switching functionality

sfp slot meaning F1118P-16-150W is a IP-COM PoE switch that offers 16 10100 Mbps Base-TX RJ45 ports, 1 101001000 Mbps Base-T RJ45 ports, and 1 1000 Mbps Base-X SFP port