Zodiac
The Zodiac is the imaginary belt of 12 sectors of 30° each in the celestial sphere, through which the Sun, Moon and planets pass. The Babylonian tradition (c. 1st millennium BC) systematized the 12 signs we know in the West: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces. The 12 names refer to constellations, but in modern tropical astrology they are 30° sectors anchored to the spring equinox.
Tropical vs sidereal
The tropical zodiac (Western) starts from the vernal equinox; the sidereal zodiac (Indian Jyotish) follows the real constellations. Differ by ~24° today due to precession of the equinoxes.