Elementalism is a section of magical practice which typically involves the use of the Platonic elements (fire, air, earth, and water) but sometimes involves other elementary substances.
The elemental initiations are carried out in order that the aspirant may come to conquer the many facets of our physical existence, as well as the psychological and spiritual impliments of each respective element. In this the novice finds himself first rooted in Malkuth, the physical world and the Qaballistic Assiah, and through steady study and practice may ascend up into higher worlds. He is confronted, however, by a wall: that of the four elements; the joint rulers of our world via all their many forms and divisions. In order to ascend into the sphere of Yesod and begin proper astral work, the expressions of the four ruling powers of the earth-world must first be brought into submission under the will, from which point they may serve as stepping stones to a great beyond.
Aside from the alchemical workings of Theurgic or Hermetic sciences, however, some magicians decide to stay with and specialize in elemental workings. This is an entirely legitimate, and emperically perhaps the most exteriorly rewarding, path for the magician to choose. The goals of such magicians usually, hopefully, pertain the achieving a degree of harmony with the forces that rule the world wherein he dominantly wanders. Such individuals truly become kings of this world, though to the eyes of men they have no crown.
For further reading into the nature of elemental and natural magic, as well as instruction in the exercise thereof, refer to "A Treatise on Elemental Magic."