The small dials or registers show, from top left and clockwise: 1. Heartbeat. There are 5 "zones" from low (50 bpm) to high (200bpm). Each zone is a 30bpm increment. You can see the radial lines in the dial increase in length clockwise from botttom right. The indicator moves in 1 bpm increments, so it shows the actual bpm, but without numbers you have to estimate the actual value. 2. Steps goal, from 0% (bottom left) clockwise to 100%. The radial lines also increase in length, and each one denotes a 10% increment. The indicator line increases by 1%. 3. Seconds indicator, from zero (double line at top left) to 60. 4. Battery level, in percent, from 0% (top right) clockwise to 100%. The radial lines also increase in length clockwise, and the indicator moves by 1% increment. As I said above, it takes some time getting used to them, but I like the minimalistic style and the radial symmetry, and a quick glance lets me roughly evaluate heartrate, steps, battery, by the color indicator lines. There's also a low battery/charge indicator. It's the lightning bolt above the battery level dial. It's normally off, when battery goes below 30% it begins to flash slowly in yellow. When it goes below 20% it flashes rapidly in red. When charging the watch, it flashes slowly in blue/greenish (teal?). AOD means Always On Display. It's an option where the watch will show the time and otherd data (depending on the watchface) after the screen timeouts. The AOD display is usually darker and refreshes less frequently than the regular display, for example, it doesn't mark the seconds. On my watch, enabling AOD reduces battery endurance from 3 to 2 days, but I prefer to have the time always available, so I keep it enabled.