Reply #2: "Don't worry, citizens! Wise-ass to the rescue!"

[DetlefK]

The symmetries he is refering to are something like the laws of conservation.

The most famous symmetries are C, P and T.
C means, that a theory/system stays the same if all charges switch signs.
P (parity) means, that a theory/system works the same way as its counterpart in the mirror.
T means, that a theory/system would still work, if time would start running backwards.

For example, P-symmetry is broken in particle reactions ruled by the Weak Interaction. They do not behave like mirror and image, but instead have the same prefered direction.
Imagine, you lift your (from your point of view) right hand and your image in the mirror would lift its (from its point of view) right hand as well...