During the Dark Ages in Europe knowledge of astrology was lost along with much other learning. It was revived and extended by Arab and Persian scholars and reimported into Europe in the Middle Ages. In medieval Europe, important political and military decisions were often made in consultation with astrologers. Nowadays, believers in astrology use it primarily for making personal decisions or attaining information about an individual through natal astrology. Today, astrology has become distinct from astronomy and mainstream scientists in general dismiss astrology as a form of pseudoscience.
The zodiac is the belt or band of constellations through which the Sun, Moon, and planets move on their journey across the sky. Astrologers noted these constellations and so attached a particular significance to them. Over time they developed the system of twelve signs of the zodiac, based on twelve of the constellations they considered to be particularly important. Most western astrologers use the tropical zodiac beginning with the sign of Aries at the Northern hemisphere Vernal Equinox always on or around March 21 of each year. Due to a phenomenon called precession of the equinoxes , (whereby the map of the night sky has changed over time), the portion of sky occupied by each of the zodiac signs no longer corresponds to that of the constellations. For this reason some Western astrologers use the Sidereal zodiac which still uses the actual star positions.
The twelve signs
In modern Western astrology the signs of the zodiac are believed to represent twelve basic personality types or characteristic modes of expression. The twelve signs are divided into four elements fire, earth, air and water. They are also divided into three qualities, cardinal, mutable and fixed. The personality traits of the twelve signs are as follows: 
- Aries (The Ram) (fire, cardinal, personal): Keyword: "I am". Freedom-loving, assertive, individualistic, independent, intellectual, pioneering, leader, action-oriented, fiery, straightforward, passionate, powerful. Can be extreme, arrogant, intemperate, violent, headstrong, impulsive. From dates March 21 to April 19.
- Taurus (The Bull) (earth, fixed, personal): Keyword: "I have". Resourceful, thorough, devoted, patient, sensual, affectionate, cautious, musical, artistic, solid, earthy, strong, sturdy, kind. Can be slow, possessive, stubborn, acquisitive, indulgent. From dates April 20 to May 20.
- Gemini (The Twins) (air, mutable, personal): Keyword: "I think". Logical, inquisitive, lively, active, curious, multi-tasking, talkative, sociable, duality, mercurial, whimsical. Can be superficial, two-faced, inconstant, restless, impulsive, headstrong, stubborn. From dates May 21 to June 21.
- Cancer (The Crab) (water, cardinal, personal): Keyword: "I feel". Protective, sensitive, tenacious, family and home oriented, helpful, nurturing, watery, emotional, loving. Can be crabby, clinging, moody, worrying, pessimistic. From dates June 22 to July 22.
- Leo (The Lion) (fire, fixed, social): Keyword: "I will". Generous, proud, theatrical, passionate, sunny, bright, kingly, powerful, loves attention, dramatic, independent, noble, creative, leader. Can be arrogant, bossy, boastful, egotistic, snobbish. From dates July 23 to August 22.
- Virgo (The Virgin) (earth, mutable, social): Keyword: "I analyze". Practical, imaginative, creative, efficient, critical, work and service oriented, common sense, modest, health conscious, mentally active, helpful, flexible. Can be pedantic, fussy, over-critical, worrying, over fastidious. From August 23 to September 22.
- Libra (The Scales) (air, cardinal, social): Keyword: "I balance". Co-operative, diplomatic, urbane, fair, needs partnerships, refined, balanced, graceful, charming, debative, just, open-minded, social. Can be lazy, indecisive, dull, rationalizing. From dates September 23 to October 23.
- Scorpio (The Scorpion) (water, fixed, social): Keyword: "I desire". Passionate, secretive, powerful, keenly perceptive, deep, complex, analytical, inquisitive, resourceful, magnetic, intense, hypnotic, sexual, perspicacious, creative, vigorous, untameable, ambitious. Can be jealous, controlling, possessive, aggressive, cunning, cruel. From dates October 24 to November 22.
- Sagittarius (The Archer) (fire, mutable, universal): Keyword: "I perceive". Freedom loving, straightforward, extrovert, philosophical, intellectual, fun-loving, arrogant, adventurous, expansive, optimistic. Can be blundering, scattered, careless, jealous, too-serious, tactless. From November 23 to December 21.
- Capricorn (The Sea-goat) (earth, cardinal, universal): Keyword: "I use". Prudent, cautious, patient, methodical, practical, reserved, ambitious, authoritative, competent. Can be saturnine, suspicious, rigid, cunning, over-cautious, pessimistic. From dates December 22 to January 19.
- Aquarius (The Water Carrier) (air, fixed, universal): Keyword: "I know". Democratic, unconventional, detached, friendship oriented, humanitarian, cause-oriented, believes in the group/society, progressive, sophisticated, trend setting, magnetic, independent, objective, opinionated, devoted to goals, outspoken. Can be eccentric, elitist, dogmatic, aloof. From dates January 20 to February 18.
- Pisces (The Fishes) (water, mutable, universal): Keyword: "I believe". Imaginative, sensitive, compassionate, feeling, idealistic, spiritual, accepting, undiscriminating, creative, mystic, self-sacrificing, artistic. Can be impractical, neglectful, escapist, lazy, distracted. From February 19 to March 20.
How important a zodiac sign is for an individual depends on the placement of planets and the ascendant in that sign. If a person has nothing placed in a particular sign, that sign will play no active role in their personality. On the other hand a person with, for example, both the sun and moon in Cancer, will strongly display the characteristics of that sign in their make up.