To define the polygon, specify an array of coordinate points:
The last point is always implicitly connected to the first. You can specify as many points, i.e. sides, as you like.
If you use longitude and latitude, specify longitude first.
$polygon operator calculates distances using flat (planar) geometry.
Applications can use
$polygon without having a geospatial index. However, geospatial indexes support much faster queries than the unindexed equivalents.