Identify the device which is shown below.
Siphon
The given device is a siphon. It works on the basis of the difference in pressure.
A portion of air inside the bottle moves out when the bottle is pressed and released. The pressure inside the bottle thus decreases. This pressure difference makes water to flow from the high-pressure to the low-pressure region. Therefore the atmospheric pressure will push the water up and thus flows through the bottle as shown below.
Let's look at other options also.
Barometer - An instrument used to measure the air pressure.
Pressure gauge - An instrument used to measure the liquid pressure.
Sphygmomanometer - An instrument used to measure the blood pressure.