The Astral Plane is a separate state of reality that is everywhere and also nowhere. Nothing is nowhere. When? Never. Nothing was never anywhere, which is why it has been everywhere. It is so everywhere you don't even need need a where. You not even need a when. That's how every it gets.
The astral plane can be accessed through astral projection, supernatural intervention, psychedelic drugs, just taking the train in New York City, and various other means. Many creatures have come to settle in the astral plane and base their lives around it.
The Astral Plane's exact size is unknown. It is estimated to be anywhere from 10 to one million times larger than the 3rd dimensional universe. The plane is split up into sub areas based on vibrational frequencies. These sub-areas can go on for infinity, but are usually classified into seven categories (each with their own seven subcategories) for convenience. These categories mirror the seven Chakras, and can be accessed through natural or unnatural means.
The Astral Plane contains a wide variety of regions with differing spiritual polarity. Differing on an infinite spectrum of magnitude, with in each sub category and sub-sub category. The measure of a spiritual being's own individual polarity corresponds to which point of polarity where they will manifest.
The Astral Plane has been notoriously hard to describe in verbal language due to its limited communicational abilities. In a survey conducted among 3rd dimensional beings who have visited the realm, many described the positively charged areas as "very bright, almost overwhelming, but very positive and relaxing," while negatively charged areas are described as "dreadful and emotionally draining."
The Astral Plane boasts no physical climactic phenomena due to its purely metaphysical makeup. Instead, emotions from higher dimensions often create regular patterns of spiritual energy flow which occur over specific areas. These phenomena are subject to change depending on the overall universal polarity of all beings.
The Astral Plane has a very diverse metaphysical environment. All entities possess a heightened level of spiritual awareness, often called Higher Consciousness (albeit possessed to varying extents). Astral beings boast various powers, including flight, teleportation, telepathy, shapeshifting, instantaneous communication, and the ability to always arrive at Mcdonalds when the milkshake machine works.