I am adding this answer because the previous ones, though correct, do not emphasize that it is the probability of interaction of the electron that waves.
According to the well-validated theory of quantum mechanics, the wave function solution of a given potential or scattering problem, $Ψ$ is complex, i.e., not measurable. It is $Ψ^*Ψ$, a real number, that can be compared with the electron position measurement, and according to the postulates of quantum mechanics, it gives the probability for the electron to be measured at (x,y,z) at time t. It is not the electron's mass or energy that is waving, i.e., have sinusoidal behavior by showing interference patterns in the single electron double slit experiment.
electron build up over time
The electron is a point particle whenever it is measured, as in the pictures above, and this assumption is checked by experiments which give very tiny limits.
The accumulation of many electrons with the same scattering boundary conditions, as in the double slit experiment, shows a wave nature, confirming the probability behavior predicted by quantum mechanics.
So the electron interacts with the potentials and boundary conditions it is subjected to, and in interacting displays a probabilistic mechanical behavior, not deterministic as in classical mechanics interactions. This probability is what is predictable (determinable) in quantum mechanics, and is responsible for what is called the "wave" nature of a particle, which can only appear under accumulated interactions with the same boundary conditions.
This also answers @rolls.