PolarPlot[r, {t, $t_{min}$, $t_{max}$}]In a Polar Plot, a polar coordinate system is used.
A polar coordinate system is a two-dimensional coordinate system in which each point on a plane is determined by a distance from a reference point and an angle from a reference direction.
Here is a 5-blade propeller, or maybe a flower, using PolarPlot:
PolarPlot[Cos[5t], {t, 0, Pi}]
The number of blades and be change by adjusting the t multiplier.
A slight change adding Abs turns this a clump of grass:
PolarPlot[Abs[Cos[5t]], {t, 0, Pi}]
Coils around a ring:
PolarPlot[{1, 1 + Sin[20 t] / 5}, {t, 0, 2 Pi}]
A spring having 16 turns:
PolarPlot[Sqrt[t], {t, 0, 16 Pi}]