the button above the econ button is manual air recirculation... so that if something smells outside or if you want to heat the car up in winter without drawing in cold air, or even cool the car down in summer without drawing in the hot air you can use that button to recycle the air already in the cabin.
the econ button is basically economy mode so no air con... why Audi would choose to do it that way i have no idea but with that light on the Air con is switched off.
the button underneath the econ is auto air recirculation which is set there for if any toxic gases are in the air around the car, the sensors would detect that and automatically switch on the auto recycle mode. of course you can manually press that button but its there to show you that the mode is on.
if you would like the proper definition that is in the handbook i can get a picture for you. but thats what they are... i was curious so i looked it up once.
also if you press the auto button in the middle is turns on the air con, and tries to control the in car air temp to the temp that is set on the display (climate control) you can then press the econ mode so that its still automatically controlling the speed of air that it uses to control the temp but just not using the air con.
if you hold the Auto button for 3 seconds it resets the passenger side temp on the climate control unit to match the drivers side so that both temps can then be controlled from just adjusting the drivers side temp control.
hope that helps