Symmetry is, for example if you draw a line in the middle of any picture, on both sides it would be equal.

Asymmetry also like symmetry, but when you draw a line in the middle of a picture it will not be equal on the different part of the line.

My photographs demonstrates these two concepts, because as you can see i have six pictures of my best photos above, three are symmetry and three are asymmetry. The top left photo is symmetry because if you put a line in the middle on both side it will be the same thing. And on the Right side, that photo is asymmetry because if u put a line in the middle there won't be the same thing on each side.