Many esoteric teachings propound the idea of a series of worlds or hypostases as cosmic ontological gradations in the Great Chain of Being, arranged metaphorically in a "higher and lower" manner.
The idea of a vertical world-axis, a cosmic mountain or tree or pole, is in fact a common archetype, and the theosophical planes are just one particular version or interpretation of that. Another is the Tantric theme of chakras, which are associated with an ascending series of states of consciousness, culminating in the Absolute Reality located either at or above the Crown. From this perspective then, the Cosmos can be divided "vertically" into a number of worlds or states or gradations of being.
Nordic and Teutonic cosmology refers to nine realms, of which the physical Earth is in the center, and called "Middle Earth" (later appropriated by Tolkein)
Since the first millennium b.c.e. Buddhist, Hindu, and Tantric cosmology has referred to a number of lokas (worlds or realms). In the Vedas (2nd millennium b.c.e.) there were three lokas - Earth, Air, and Heaven, which became seven with the Puranas. Buddhism refers not just to five or six realms of rebirth, but also a large number of "deva lokas" or heaven realms, which are identified with both traditional cosmology (including Mount Meru, the world axis) and states of meditation.
Beginning with Middle Platonism and Neopythagoreanism and continuing through to Gnosticism, Neoplationism, Sufism, Kabbalah, and Rennaisance Hermeticism are visionary angelological or divine worlds or universes, each higher of which emanates the one below it, Light becoming form (Suhrawardi, Luria, etc) until we are left with the objective physical as the most "dense" reality. The idea of the congealing of consciousness occurs in Shaivite and Shakta Tantra (the Tantrics use the example of milk that forms curd (ref Arthur Avalon/John Woodroffe ref xxxx)).
From the 19th onwards, the term "Planes" has been used by Theosophy, and from there off-shoot esoteric systems (such as Alice Bailey) and the New Age movement, as well as Eastern teachings that have some Western influence (e.g. , Sri Aurobindo and Sant Mat) to describe these gradations. The originator of this popular occult term is H.P. Blavatsky, who in The Secret Doctrine and elsewhere taught a complex cosmology consisting of Planes and subplanes. However the original source of the term is the late Neoplatonist Proclus, who refers to to platos, "breadth", which was the a term direct equivalent of the Theosophical use. e.g. en to psuchiko platei [Dodds, cited in Poortman, Hylic Pluralism, vol II, p.54]. Through Theosophy, the idea of Planes of Existence has even entered everyday langauge - e.g. "the astral plane". Theosophical and, following them, New Age, cosmologies speak of seven "planes of existence"; each of these in turn often subdivided into further planes and hypostases. According to Madame Blavatsky, there are seven "kosmic" planes, each divided into 7 further planes (the lowest kosmic plane being made up of seven "prakritic" planes), each of which is divided into seven conventional planes, each of which in turn is made up of seven subplanes. That gives 74 subplanes, or 2,401 altogether, although only the last few series of planes (and occasionally subplanes) are really described at all.
Very similar is the Tradition of Max and Alma Theon, with four worlds (this seems to be based on Kabbalah) of which the lowest or Material World is made up of eight "states", although only the lower four are really described and considered (the higher four presumably pertaining to transcendent states). Each of these lower four (the higher four not being considered here) is made of four degrees, and each of these in turn consists of four subdegrees, which presumably were in turn sub-divided. According to Mirra this was an excellent descriptive tool, and one could, by working on an undeveloped sub-sub-part of the being eventually break through and access occult or spiritual experiences [I forget the reference, it is in one of the early volumes of the Agenda]
Sri Aurobindo, whose metaphysical and spiritual insights and roadmaps of conscioousness have inspired a lot of my own understanding, refers to this as a vertical or ascending scale of consciousness. However, despite the widespread use of this metaphor, I am reluctant to give too much emphasis to the word "vertical" here. The reason is that the experience of a vertically arranged hierarchy of planes may very well simply be a side-effect of the organisation of the human physical and etheric body. A quadrapedal animal for example has chakras arranged horizontally, and so would experience these planes as horizontally organised. Hence my use of inverted commas when referring to this.
Gurdjieff's scale of "hydrogens" in the "ray of creation" is another version of the same thing. Other terms used are "worlds", lokas, etc. The term Octaves - another Gurdjieffian term, adapted from Gurdjieff's incorporation of the musical scale in his ray of creation - is also useful, as it refers to the fact that at each hypostasis, each plane of existence, there is a full complement of subplanes (Theosophy) or resonances, which fractally repeat the whole.