Instead of being planar, cyclohexane twists into something called a chair conformation to reduce angle and torsional strain.
By twisting into a chair, angle strain and torsional strain are now effectively zero.
Concept: How chairs flip from one conformation to another3m
In order to flip from one chair to another, the cyclohexane must first pass through a boat conformation (not stable due to flagpole interactions of hydrogens!).