can anyone explain the way an "oldschool" windmill works?

Don't need to be big to make electric

 

Art

 

The old Aeromotor windmill at the home place was on about a 50 ft tower with about 10 ft wheel and as near as grand dad could find out put out about 1/4 horsepower at 15 mph wind. Pumped water into the tank and gravity brought it to the buildings. Had a hand pump on it, the windmill pump rod connected to the hand pump and could be disconnected to allow hand pumping. The neighbors had pump jacks, required a motor to turn a pulley to pump when the wind didn't blow. Was expensive, big, not very efficient, required service to the head every few years and that was 50 feet up a tower to a very small platform, only really worked if wind was over 10 mph and less than about 30 mph, but supplied most of the water needed on the farm for 100 + years with a use of about a quart of oil every few years. As near as I can figure out, with some care, might still be good for the next 100 years. There is a spare wheel and leathers etc in the shed so have parts for at least 25 years on farm now.