1000 Megabit Ethernet (1000Base-T) is a standard for Gigabit Ethernet over copper twisted pair cables. It was first defined by the IEEE 802.3ab standard in 1999 and has been widely adopted in both home and office networks. 1000Base-T uses all four pairs of wires in standard CAT-5 or CAT-6 cabling to achieve full Gigabit speeds, up to 1000 Mbps.
While most home users will never need the speeds that 1000Base-T provides, it can be very useful for businesses who need to move large amounts of data quickly between computers on a LAN. For example, if you have a file server with several hundred gigabytes of data that needs to be backed up nightly, using 1000Base-T can reduce the time required for the backup process from hours to minutes.
If you are planning on upgrading your network to Gigabit speeds, then 1000Base-T is likely the best option available today. It is compatible with existing CAT-5 and CAT6 cabling infrastructure and offers very good performance at reasonable prices.