The Zodiac is a family of constellations that lie along the ecliptic (the plane in which most of our Solar System lies). Usually, 12 constellations are listed in the Zodiac, but there is actually a thirteenth constellation that crosses the ecliptic, Ophiuchus (between Scorpio and Sagittarius).

Aries, the ram
Taurus, the bull
Gemini, the twins
Cancer, the crab
Leo, the lion
Virgo, the virgin
Libra, the scales
Scorpius, the scorpion
Sagittarius, the archer
Capricorn, the goat
Aquarius, the water bearer
Pisces, the fish