|duplex||Refers to the ability to transfer data in both directions. Full-duplex allows for data transfer in both directions simultaneously; half-duplex allows for data transfer only in one direction at the same time.
Most current NICs allow for full-duplex communication, theoretically doubling their throughput (i.e. for 100BaseT - 100 Mbps in one direction and 100 Mbps in the other at the same time). Curent Cable/DSL modems are usually half-duplex.