Do gigabit ports have a total throughput of 1 gigabit so that you could be sending 800 mbit and receiving 200 mbit at the same time. Or is it 1000 in and 1000 out?
That depends on whether you're running in half duplex (1 gigabit total) or full duplex (1 gigabit each direction). Of course, you'll never hit these theoretical performance limits.
It's not quite as simple as that, but yes, GBe is full duplex, so data can flow in both directions simultaneously.
If the switch backplane supports it, you should be able to get ~1 Gbps inbound AND outbound. The major limiting factor is the switch backplane and if that only supports 1 Gbps, you'll get packet loss, but if it's sufficiently fast, you'll be able to get a higher aggregated throughput through the switch.