Polygon
[{$point_1$, $point_2$ ...}]Polygon
[{{$p_11$, $p_12$, ...}, {$p_21$, $p_22$, ...}, ...}]A Right Triangle:
Graphics[Polygon[{{1,0},{0,0},{0,1}}]]
Notice that there is a line connecting from the last point to the first one.
A point is an element of the polygon if a ray from the point in any direction in the plane crosses the boundary line segments an odd number of times.
Graphics[Polygon[{{150,0},{121,90},{198,35},{102,35},{179,90}}]]
Graphics3D[Polygon[{{0,0,0},{0,1,1},{1,0,0}}]]