The Ethereal Plane is one of the plane existing in the universe. It co-exists with the material plane, You can see the Material plane from the ethreal, However edges are blurred and you cannot see finer details. Hearing things from the material plane are muted aswell. You cannot interact with anything of the material plane neither can they with you. People in the material plane will not see you hear you or know abotu your presence in any way. If useing Ethereal Jaunt to get there you are put into a Ethereal body, When you use the spell again you go into your body which will be where you casted the spell at. This is a useful plane for spying, Some measure can be used to stop spys from the ethereal plane. Fog ecompesses your sigh for 60 feet. It is dimily lit on its own. If you wish to travel here it is recommended you do some additional reserch as this is the bare basics.