A circle.
Yes, the simplest definition of a mandala is just that. It means “circle” in Sanskrit. Maybe that’s why they are probably circular shaped.
Of course that’s not its only meaning. It also means circular, sphere, ring, group, collection, body, society, part, section and chapter.
Mandala is made out of two words. “Manda” and “La”. Manda means “essence, truth, energy”, while La means “container, hold, area”.
When you combine them, you get a more meaningful definition: The container of essence.
This definition could be applied to another example we all know. Something that has a soul on one hand, and a container that holds the soul, a.k.a. a body, on the other.
Human beings.
When you look at it that way, mandalas represent human beings.
The mandala you draw reflects you. You can tell a lot about yourself by looking at the colors you use, the patterns you draw, and the drawing style you apply. You can even go deeper and bring out what you have on your subconscious.
However, if none of these interest you, you can look at the mandala from a different angle: A tool that will separate you from the daily chaos, even for a short while, and let you calm down while creating a masterpiece.