I was reading a book about electrodynamics.
the book said
we shall now consider the special case when 'the scalar potential' and the field component depend harmonically on the $z$ coordinate (along a steady magnetic field), i.e., when 'scalar potential' and the fields contain one of the following functions (or a linear combination of them)
$\exp(i\beta z)$, $\exp(-i\beta z)$, $\sin(\beta z)$, $\cos(\beta z)$.
I don't understand what 'harmonic dependence' means. Does it mean kind of 'periodic'? or 'harmonic function' that satisfies Laplace's equation?