Self-adjoint operator

A self-adjoint operator is something you can use in maths. It is like a two-sided ruler - you can use it to measure things in both directions. In this case, the self-adjoint operator measures something called a 'vector' in two ways - it makes sure that a vector is the same when flipped around (like a two-sided ruler). This helps us understand how certain mathematical calculations and equations work, and it helps us solve problems.