What are geometry primitives in GeoJSON?

In Eucledian geometry we were taught about the concepts of 'Point' and straight line being the shortest distance between two points.

GeoJSON is an Open Standard format based on JavaScript Object Notation for representing simple geographical (geometrical?)features.

In GeoJson Point, Line and Polygon are the Geometric Primitives:

Point:
{ "type": "Point",
    "coordinates": [30, 10]
}
Line:
{ "type": "LineString",
    "coordinates": [
        [30, 10], [10, 30], [40, 40]
    ]
}
Polygon:
{ "type": "Polygon",
    "coordinates": [
        [[30, 10], [40, 40], [20, 40], [10, 20], [30, 10]]
    ]
}
This post is based on GeoJSON on Wikipedia.