When you're awake, you're conscious and aware of your surroundings. When you're not awake, you're asleep. If you are reading this, you are indeed awake.
Most people are awake during the day and asleep at night, but if you work the night shift or suffer from insomnia, you might also be awake at night. When awake is used as a verb, it means "wake up:" "I watched my kitten awake from a deep sleep and yawn." Awake comes from two Old English roots, āwæcnan, "to arise," and āwacian, "to revive."