My understanding is that gigabit Ethernet over twisted pair, 1000Base-T, is full-duplex by default. Does that mean that the actual bandwidth, can be 1 Gbit/sec in each way simultaneously, hence 2 Gbit/sec counting both ways?
In comparison, Wi-Fi is half-duplex on each channel, meaning a 800Mbit/sec connection can only achieve that number in one-way at a single time.
So the max bandwidth for wired Ethernet connection can actually double that of Wi-Fi, for the same claimed bandwidth?
Full duplex means bidirectional communication. So yes it could in theory reach 1 gig up and 1 gig down, but the device transmitting up or down would still only reach a max of 1 Gpbs.
Reaching the theoretical max would also depend on the NIC and other hardware such as drive IOPS. Don’t hold your breath too hard if you don’t actually ever see the potential bandwidth being 100% utilized.
Expanding on DrZoo's answer, it depends on your applications utilizing the network connection. In layman's terms: e.g. if you do "up- and downloads" at the same time (e.g. via two independent sessions) you will "fully" utilize the full duplex but most of the times this is not the case.
Especially if you only use one session, there it's mostly either sending or receiving at "any given moment" (except for maybe the "occasionally send out the acknowledgement message" for a received data chunk while still receiving new data chunks but which doesn't eat much "bandwidth" anyway).
