You can see on the screen shot that there are places for lots of information about a UPS, but not all of them are filled in. This is because the various makes and models report very different information, depending on their capabilities. For instance, the little shoebox-sized test unit I have on my desk has very different capabilities than (say) a gigantic Liebert UPS that has two independent connections to the mains and two diesel backup generators connected! So depending on the make and model being explored, Discovery will fill in everything it can find out — which may be far from a complete screen.
Discovery finds this information through SNMP. Like there is for many kinds of equipment, there is a standard MIB for UPSs: the UPS-MIB. Most UPS companies do a good job supporting this standard MIB — but unfortunately the behemoth in the category (American Power Corportation, aka APC) decided not to use the standard MIB, so Discovery also has to explore their proprietary MIB as well (the PowerNet-MIB). Both MIBs have very similar information, so we were able to make a single form and lists to support them all.
Most of this screen will be obvious to you if you know anything about UPSs — but one related list might be a little mysterious: the bypass list. A bypass is a feature of some UPSs (they're especially common on larger datacenter-class UPSs) that allows the UPS to connect an input directly to an output, thus letting the power flow "bypass" the UPS itself.
Not showing on the screen (because it wouldn't fit!) is another related list of UPS alarms. There are dozens and dozens of different alarms possible, ranging from the mundane (like "my battery is getting hot!") to the very urgent ("the main power is out and I only have 3 seconds of battery left!").
