Although there are variations in the details, it is commonly claimed that there are seven great planes and seven corresponding bodies or vehicles. The grossest of all is the physical body, of flesh, with which we are all familiar. Etheric double is the manifestation of physical vitality. It is constant and does not change throughout the cycles of life and death, but it is not eternal, for it is eventually re-absorbed into the elements of which it is composed. This 'double' acts as a kind of transmitter of energy, keeping the lower physical body in contact with the higher bodies.
Etheric substance is seen as an extension of the physical.
These entities are thought to be finer than their etheric counterparts and correspondingly harder to see. The astral world consists of astral matter, and all physical objects have a replica in the astral. There is therefore a complete physical copy of everything in the astral world, but in addition there are things in the astral which have no counterpart in the physical. There are thought forms created by human thought, elementals and the lowest of the dead, who have gone no further since they left the physical world. All these entities and many others are used in ritual magic, and thought forms can be specially created to carry out tasks such as healing, carrying messages, or gaining information.