Early Ethernet LAN’s were running at 10 Mbps (Megabits per second) speeds. Then we had FastEthernet operating at a speed of 100 Mbps (Megabits per second). Later at 2010 beginning, Gigabit Ethernet operating at speeds of 1000 Mbps (Megabits per second) or 1 Gbps (Gigbits per second) started to replace FastEthernet. Ethernet standards are renewed periodically, as IEEE (Institute of Electrical and Electronics Engineers) releases new standards on Ethernet.
Following picture shows a 48-port Cisco 10/100/1000 Ethernet Switch.
Following picture shows a 10/100/1000 Ethernet NIC.
We can say an Ethernet network interface Card (NIC), an Ethernet network switch or a router’s Ethernet interface is 10/100/1000, if it can transmit data at all Ethernet (10 Mbps), FastEthernet (100 Mbps), Gigabit Ethernet (1000 Mbps speeds).
Please note that above pictures are not in scale.