Symmetry is a mathematical concept where an object appears identical after some transformation such as reflection, rotation, or translation. Geometric shapes with symmetry appeal to our visual perception. Tessellations are patterns made of shapes that fit together without gaps. Symmetry is important in fields like chemistry for understanding molecular structures, in art for creating balance, and in music where symmetrical patterns can sound pleasing. The document discusses definitions of different types of symmetry and applications in areas like science, art, and music to highlight symmetry's significance.