Explain 4 types of pressure

Here are four types of pressure:

1. Absolute Pressure: This is the pressure measured relative to a perfect vacuum (zero pressure). It includes the atmospheric pressure. For example, a tire pressure gauge reading of 30 psi (gauge) would be approximately 44.7 psi (absolute) at sea level.
2. Gauge Pressure: This is the pressure measured relative to the ambient atmospheric pressure. Most pressure gauges, like those for car tires or air compressors, display gauge pressure. A positive gauge pressure indicates pressure above atmospheric, while a negative gauge pressure (vacuum) indicates pressure below atmospheric.
3. Atmospheric Pressure: This is the pressure exerted by the weight of the air in the Earth's atmosphere. It varies with altitude and weather conditions. At sea level, standard atmospheric pressure is approximately $101.325 \text{ kPa}$ or $14.7 \text{ psi}$.
4. Differential Pressure: This is the difference between two pressures. It is often used to measure flow rates, liquid levels, or filter conditions in industrial applications. For instance, a differential pressure sensor might measure the pressure drop across an orifice plate to determine fluid velocity.