How does a siphon work

Gasoline siphoned from a tank flows up the tube on its way out of the tank before descending through the tube's other end into a waiting can.
How does it work? First, a few conditions must be met.
The gas tank has to be open to the atmosphere.
The receiving can must be lower than the gas tank.
And the tube has to be filled by suction or some other method to get the flow started.
The process begins with gas falling by force of gravity from the filled tube into the can.
This creates a lower-pressure zone at the bent top of the tube.
The gas at the bottom of the tank , meanwhile, is under the combined pressure of the air and the gas itself.
This high pressure pushes the gas up to the lower-pressure area at the top of the tube.
Siphon have been employed since ancient times.
The Egyptians and the Greeks were the first to use them.