Cisco Pluggable (sfp) Gigabit Interface Converter

Hot-swappable input/output device that plugs into a gigabit ethernet port or slot, linking the port with the network
Sfps can be used and interchanged on a wide variety of products
Can be intermixed in combinations of 1000base-t, 1000base-sx, 1000base-lx/lh, 1000base-ex, 1000base-zx, or 1000base-bx10-d/u on a port-by-port basis