Reflectional and rotational symmetry
The idea of symmetry comes up a lot in art and design. It is an important idea in maths too. People are attracted by symmetry. Human faces have one line of symmetry, which is down the middle with an eye and an ear either side.
In art, symmetry can be just part of a design or it can be the most important feature.
Simple symmetry can make designs feel calm and disciplined. However, symmetry can also be very complicated, with many lines of reflection. Symmetry can also be rotational, like the amazing geometry of Islamic art.