Are the electron shell and the electron cloud the same thing?
One is 2D, the other 3D.
An electron shell is like a ring around the nucleus of an atom. On that ring or shell, electrons travel around the atom. That is a 2 dimensional look at at atom and the electrons orbiting around it.
However, it is not 2 dimensional. Electrons orbit in different directions and at different angles. The fact that they're orbiting every which way and they orbit with such speed, it is impossible to predict where any one electron will be at any one specific time. They seem to travel so quickly and at so many angles, it all kind of blurs together giving a cloud effect, hence the name electron cloud.