Polygons are a lot like polylines in that they're composed of straight line segments connecting a list a points. For polygons though, the path automatically returns to the first point for you at the end, creating a closed shape. Note that a rectangle is a type of polygon, so a polygon can be used to create a <rect/>
element in cases where you need a little more flexibility.
<svg xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink">
<polygon points="50 160, 55 180, 70 180, 60 190, 65 205, 50 195, 35 205, 40 190, 30 180, 45 180"/>
</svg>