Spica is Alpha Virginis, the brightest star in Virgo, apparent magnitude 0.97, at about 250 light years. The Latin name means the ear of wheat, which is what the Virgin holds in the constellation figure.
Its physical nature is not what the eye suggests. Spica is a close binary of two hot blue stars, spectral types around B1 and B2, orbiting each other in four days at a separation so small that they are distorted into ellipsoids by mutual gravity. The system varies slightly in brightness as these distorted shapes present different areas to us, a rotating ellipsoidal variable, and the primary is also a Beta Cephei pulsator. Neither component is resolvable; everything known about the pair comes from spectroscopy and photometry.
Spica's historical importance is out of proportion even to its brightness. Hipparchus, in the second century BC, compared his own measurement of the star's position relative to the autumn equinox with earlier Babylonian and Greek records and found a discrepancy of about two degrees. From that discrepancy he inferred the precession of the equinoxes. It is one of the foundational discoveries of positional astronomy, it was made using this star, and it is the reason every zodiacal position quoted in an old text has to be dated before it can be used.
Spica lies close to the ecliptic, about two degrees south, and is occasionally occulted by the Moon and rarely by planets.
Spica is among the stars proposed as an alignment target for Egyptian temples, and Norman Lockyer argued in the late nineteenth century that a temple at Thebes was oriented to its setting and readjusted over centuries as precession shifted it. That reconstruction is contested, and archaeoastronomical alignment claims generally need more caution than they receive.