The electron is in reality not a point particle, but is spread out in space. The function we use to describe it is also spread out in space, and upon changing reference frames, the shape of this function can stretch as well. You can imagine it a bit like a cloud which changes shape depending on the reference frame you are in. However, mathematically, it is more $\mathbb{C}$omplex than that, and I have only written an analogy to physicists' description of a particle.
If you are curious to learn what exactly is spread out in space: roughly, it is a probability density. More accurately, in quantum mechanics, the object we use to predict experimental outcomes on particles is a function $\psi(x)$ which assigns a complex number to each point in space.
Above is a picture of an electron cloud in different configurations, within a hydrogen atom. Even though the cloud extends throughout ALL space, this picture highlights the area with the highest probability.