There are three connectors (depressed circles with metal inside) on the tablet, and three protruding pieces of metal on the keyboard case. They go together. There are also two depressions on the tablet that match with two tabs on the keyboard -- appear to be plastic and I think are just for alignment. It started working immediately; no reason to believe there's a battery.
And bonus: While the pen seems nice, it was often getting knocked off, and I scrambled to find it, and I was thinking that this is going to be gone soon. The case covers it nicely, and it folds out to allow you access to it. So maybe it won't get lost so fast.
The cover is really two pieces. One forms the bottom of the tablet, covers the pen, and is the source of that stand you see pictured all the time. The tablet does not have the stand -- it's the case. THEN you can put the edge of the tablet into the place at the back of the keyboard (likely only with that bottom, but you'd need it anyway to prop it up when using it in that mode). Connect it, and it turns on the tablet (at least if it's asleep -- guessing it won't do that if it was powered off). Also, close it, and the tablet sleeps; open it and it wakes up. (OR at least the display goes off and on; not sure, if you had something running, if it'd keep running. I think it's the same as whatever happens when you tap the power button.)