Geometry in Databases

There is a whole set of functions available to work with geometry in SQL Server. Geometry refers to objects with coordinates on a flat map. This is different than geography, which uses a globe and takes the curvature of the Earth into account. Geometry is fine if you are not dealing with huge distances.
Geography is more complex than geometry. You reference location via longitude and latitude.

In geometry, you have x and y coordinates. Pair them up and you get a point. The points can be used as endpoints for more complex objects. Once you have points or other objects, you can compute relations between them such as distance and intersection.

Once you have geometry objects, you can aggregate them together. That means combine lesser objects to form another one that encompasses the source objects. The result can be a short of outline that fits all the source objects.