What is a Symmetry Element versus What is a Symmetry Operation?

Recall that H₂O has 4 Symmetry Operations: E, C₂, &sigma_YZ and &sigma_XZ
Using the C₂ and the &sigma_YZ as examples:

1. For the C₂:
   The C₂ Axis is the Symmetry Element about which we will do the 180^o (C₂) Symmetry Operation.
   
   • The Symmetry Element: Show the C₂ Rotational Axis
   • The Symmetry Operation: Carry out the C₂ Operation
2. For the &sigma_YZ Operation:
   The &sigma_YZ Plane is the Symmetry Element across which we will carry out the &sigma_YZ Symmetry Operation
   
   • The Symmetry Element: Show the YZ Reflection Plane
   You may move the molecule to any position to observe the YZ Reflection
   
   • The Symmetry Operation: Reset (if needed) then Carry out the Operation of Reflecting Across the YZ Plane
     The result of this operation was to interchange the H_a and H_b atoms
In Summary: A Symmetry Element is a Geometric Entity (a line, plane or point) about which
we carry out a Symmetry Operation (operating on the molecule: rotating it in space, refecting atoms (or part os atoms) across a plane, etc.