The difference between 'Elevation' and 'Depth'

Both the terms ‘elevation’ and ‘depth’ describe the vertical position of points on the earth’s surface as measured from the mean sea level. However, the term elevation is mainly used when referring to points above the sea level, and depth is used for points below the surface

The elevation is the vertical position of points above the mean sea level.

whereas 

The depth is the vertical position of points/objects below the mean sea level.

Recommended: The difference between 'Elevation' and 'Altitude'.