This classic symbol, from ancient Buddhist teaching, depicts the endless (until you practice!) cycle of suffering — birth, ageing, sickness, and death, repeat — sometimes called “samsara”. It is a teaching about the hard-fact of impermanence of all conditioned states, both those of the physical world (obvious) and of the mental (not so obvious to most).
First, a more traditional wheel, from Tibet:
I post this because these modern adaptations give a very interesting updating of the teaching, addressing the modalities of impermanence in our hectic daily lives in the modern world, awash in a sea of consumerist opportunities: