As you might know, the earth and most people occupy the 3rd dimension. But if you are awakened, you probably occupy the 4th dimension at times or all the time. The 4th dimension connects the 3rd dimension (humans) and 5th dimension (spirit) together. Dreams – the unconscious – occupies the 4th dimension. While we dream, we can astral project and temporarily leave out bodies and travel to the 4th & 5th dimensions. The 4th dimension has multiple layers broken down below from lowest to highest. (taken from multidimensions.com
Lower astral – mastery over fear / negatively (what is equated as Hell / purgatory)
Land of faerie – playful / silly – combination of emotional / mental / spiritual
Astral / emotional – mastery over emotions
mental – mastery over thoughts
casual / spiritual – cause and effect / spiritual guidance
In dreams, nightmares can come from the lower astral and crazy & silly dreams from land of faerie. (food for thought – if some ancient civilizations operated at a 4th dimensional level, explains origin of fairy tales via land of faerie.)
The 4th dimension is very balanced – if you approach it with openness, respect, and love – you will reach the upper 4th dimension, but if you are full of fear and baggage, you will only occupying the lower 4th. I personally experienced this in a recent astral dream. I had to get through scary ridiculous dreams to get to a premonition about a possible kidnapping. I was traveling through the lower astral – part of me knew I had to keep going / digging to get to the other side.