Pisces

Pisces (♓) is the twelfth astrological sign in the Zodiac, which originates from the Pisces constellation. In western astrology this sign is no longer aligned with the constellation because of the precession of the equinoxes. In astrology, Pisces is considered a "feminine", negative (introvert) sign. It is also considered a water sign and one of the four mutable signs. Pisces has been traditionally ruled by the planet Jupiter, but since its discovery, Neptune has been considered a modern ruler of this sign. Being the twelfth sign, Pisces is associated with the astrological twelfth house.

Individuals born when the Sun was in this sign are considered Pisces individuals. Under the tropical zodiac, the Sun is in Pisces roughly from February 20 to March 20, ending on the moment of vernal equinox by definition. Under the sidereal zodiac, it is currently there roughly from March 15 to April 13. The Sanskrit name of Pisces in Hindu astrology is Mīna.

Based on Elements within the Zodiac, Pisces is considered compatible with Scorpio, Cancer and Pisces itself.
There are many variables that determine compatibility in astrology, such as birth dates, birth months, birth years, position of a sign within the Sun, the Moon, Stars, etc. The signs listed as compatible with Pisces do not reflect an individual profile or individual reading as interpreted within astrology, but rather reflect a general guideline and reference to compatibility as dictated by variables such as Qualities and Elements within the Zodiac. The branch of astrology dealing with interpersonal compatibilities is called Synastry.

Source : http://en.wikipedia.org/wiki/Pisces