Who decided the constellations in the night sky, and how? What we casually call "my sign" refers, more precisely, to one of twelve regions laid out along the Sun's path—the ecliptic. As the Earth circles the Sun over a year, from Earth it instead looks as if the Sun slowly crosses among the stars. Dividing this solar path into twelve and naming each region after the cluster of stars within it gives us the zodiac, running from Aries to Pisces.
Seen this way, it becomes natural to understand why your sign depends on your birthday. Your "Sun sign" is set by which region of the ecliptic the Sun was passing through on the day you were born. Astrology treats the Sun sign as so important because the Sun is held to symbolize a person's sense of self, their core life energy, and the direction in which they wish to shine. The pride we associate with Leo or the care with Virgo arises precisely from this seat of the Sun.
Real astrology, however, does not end with the Sun sign alone. It also reads where the Moon, Mercury, Venus, Mars, and other planets sat along the ecliptic at the moment of birth, painting the many textures of life in three dimensions—the Moon for emotion, Mercury for communication, Venus for love, Mars for action. So even two Leos, one with the Moon in Cancer and another with the Moon in Scorpio, hold entirely different inner landscapes. "What sign are you" is only the first coordinate on a vast map; on its own it cannot fully describe a person.
To know your sign is, in the end, to read the shape in which the great clock of the sky stood still at the moment you were born. When you treat that coordinate not as a fate that confines you but as a mirror reflecting the grain of your innate temperament, your strengths, and the parts worth nurturing, a horoscope becomes a delightful language that helps you understand yourself more generously. FortuneLeaf's zodiac content is written in just that spirit—unfolding the sky's coordinates as gentle advice handed to the you of today.
If a sign speaks of "with what temperament," a house points to "on which stage of life" that temperament unfolds. The birth chart is a round map of the sky at the moment of birth, and dividing that map into twelve sectors gives the houses. The first house treats the self and first impressions; the second, money and values; the fourth, home and roots; the fifth, romance and the joy of creation; the sixth, work and health; the seventh, partnership; the tenth, career and social achievement. Depending on which planet sits in which house, the energy of the same sign may stand out in love or shine in work. This is why a seasoned astrologer does not stop at "what sign" but also reads "which room of life that star has entered." Once you know the houses, a vague sign reading at last settles onto the concrete places of your own life.