Fuel Tank Quantity and Fuel Tank Selection - Shows quantity of tanks and which tank is currently selected. You can run in auto mode which will select tanks for CG balance.
Surface Trim Indicators - Shows position of rudder, elevator and aileron trim tabs
Accelerometer - Number of G's aircraft is pulling
Beacon - Shows your connection status to the host
Grayed out - Nothing wrong
Green - Slight variance
Yellow - Problem exists
Red - Your connection is being lost
Landing Gear Indicator - Green indicates gear down, grayed out indicates gear retracted, yellow indicates gear in transit.
Clock - Shows current server time if online, adjusted time if set offline