In the mature Theosophical scheme worked out by Charles Webster Leadbeater and Annie Besant in the early twentieth century, the astral body, or kama rupa ("desire form"), is the layer of subtle matter corresponding to emotion, desire and passion, positioned in the sequence of bodies above the etheric double, which is tied closely to physical vitality, and below the mental body, tied to thought. This was a deliberate refinement of earlier, looser Theosophical usage: Helena Blavatsky and other early writers had sometimes used "astral body" for what Leadbeater and Besant would later insist on calling the etheric double instead, and part of Leadbeater and Besant's contribution was fixing this more precise, consistent terminology for the movement going forward.
Astral energy, in this scheme, is the animating force of emotional life and is closely associated with claimed psychic phenomena, most prominently astral projection, or astral travel, in which the astral body is described as capable of separating from the physical body, typically during sleep, trance or deliberate meditative practice, and perceiving or moving independently of physical constraints. Leadbeater's own detailed, clairvoyantly derived descriptions of astral matter, color and structure, published across several of his books in the early 1900s, remain the most extensive primary Theosophical source on the astral body's claimed properties.