You step into the border regions of the Ethereal Plane, in the area where it overlaps with your current plane. You remain in the Border Ethereal for the Duration or until you use your action to dismiss the spell. During this time, you can move in any direction.

What is the point of Etherealness?

The Etherealness spell states: You ignore all objects and effects that aren't on the Ethereal Plane, allowing you to move through objects you perceive on the plane you originated from. When the spell ends, you immediately return to the plane you originated from in the spot you currently occupy.

Can you end Etherealness?

Yes.

There is nothing inherent to the Ethereal plane that prevents rest.