Just as there are 12 signs in the zodiac there are also12 houses. The following anology best capsulates what are the signs, planets and houses. The houses can be seen as a stage and props that are to be used in a theatrical play. The planets are its actors. And the signs form the backdrops.
Western astrology uses the elements fire, earth, air and water to define the essence of the signs.
Each sign is assigned an element. Distibuted through the 12 signs, three sets of 4 signs contain the same element. The 4 signs that make up each set of the same element are known as a triciplicity and denote a particular harmonious form. However, the elements themselves may take on various forms. For example, water can take on the form of a river, lake or even an ocean.