Here's a breakdown:

* Height: Elevation measures the vertical distance of a point compared to a specific base point.

* Reference level: The most common reference level is mean sea level (MSL). This is a global average of the sea level, calculated from numerous tide gauge measurements.

* Above or below sea level: Elevations can be positive (above sea level) or negative (below sea level). For example, Mount Everest has a positive elevation, while the Dead Sea has a negative elevation.

Why is elevation important?

Elevation plays a significant role in various aspects of our planet:

* Climate: Higher elevations generally have colder temperatures, lower air pressure, and less oxygen.

* Geography: Elevation impacts the formation of mountains, valleys, and other landforms.

* Ecology: Different plants and animals thrive at different elevations due to varying environmental conditions.

* Human activities: Elevation is crucial for construction, transportation, and other human activities.

How is elevation measured?

Elevation is measured using various techniques, including:

* GPS: Global Positioning System devices use satellites to determine precise coordinates, including elevation.

* Surveyors: Surveyors use specialized instruments like levels and theodolites to measure elevation differences.

* Barometric altimeters: These devices measure air pressure, which varies with elevation.

Understanding elevation is essential for understanding the Earth's geography, climate, and environment.