Atmospheric pressure is the force exerted by the weight of the air column above a given point. At sea level, this averages 1013.25 hPa (hectopascals), equivalent to about 10.3 tonnes per square metre — a force we don't feel because it acts equally in all directions and our bodies are adapted to it. Pressure decreases with altitude at roughly 1 hPa per 8 metres near the surface, which is why barometers must be corrected to sea-level equivalents for weather analysis.
Variations in atmospheric pressure drive the wind. Air flows from areas of high pressure (anticyclones) to areas of low pressure (depressions), deflected by the Coriolis effect so that it spirals rather than flowing in straight lines. The greater the pressure difference (gradient) over a given distance, the stronger the wind. On weather maps, pressure is depicted by isobars — lines of equal pressure — that reveal the pattern of highs, lows, ridges, and troughs.
Pressure changes are the foundation of weather forecasting. A rapid drop (>3 hPa in 3 hours) warns of an approaching storm or depression. A steady rise indicates improving, more settled conditions. The lowest sea-level pressure ever recorded was 870 hPa in Typhoon Tip (1979), while the highest was 1084 hPa in Agata, Siberia (1968). Modern digital barometers — including those embedded in smartphones — make pressure data universally accessible for anyone interested in weather observation.