A galaxy is a large assemblage of stars, gas, and dust bound by gravity. Galaxies come in three basic flavors: spiral, elliptical, and irregular.
The easiest galaxy to observe is our home galaxy, the Milky Way. From mid-Northern latitudes the brightest galaxies include the Andromeda Galaxy (M31), Bode's Galaxy (M81), the Whirlpool Galaxy (M51), the Spindle Galaxy (NGC 3115), and the Sombrero Galaxy (M104).