If we add the moon sign, we extend the range of categories to include the 12 possible sun signs in combination with the 12 possible moon signs, and increase the possibilities to 144. The twelve signs are a combination of expressed energy that can be classified via their relationship to the four elements and three modes. I will discuss the elements more thoroughly in a moment, but I will begin with the classification of the signs via their modes. In the language of astrology, the birth phase or initiating phase is referred to as the cardinal mode, the continuity of existence or maintenance phase is referred to as the fixed mode and the transformative phase or changeable phase is referred to as the mutable mode. Each sign of the zodiac is expressed through one of these three modal phases as well as one of the four elemental forces.
Fire is an active and forceful energy.
The zodiac's fire signs, Aries, Leo, and Sagittarius then, are all representative of an energetic, passionate, self-directing and assertive character because they are all signs representing the fire element. The earth signs, Taurus, Virgo and Capricorn, all demonstrate reliable, practical and sensual characteristics. The air signs, Gemini, Libra and Aquarius endow one with a mental, communicative, and social character and the water signs, Cancer, Scorpio, and Pisces represent emotional, sensitive, and receptive traits. This is, of course, a very simplified accounting of the modes and elements. The important point is, your understanding of these elements as you've experienced them in everyday reality, will assist you in understanding their symbolical association to the twelve signs of the zodiac.