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In astronomy, the habitable zone (HZ) is the distance from a star where an Earth-like planet can maintain liquid water on its surface[1] and Earth-like life. The habitable zone is the intersection of two regions that must both be favorable to life; one within a planetary system, and the other within a galaxy. Planets and moons in these regions are the likeliest candidates to be habitable and thus capable of bearing extraterrestrial life similar to our own. The concept generally does not include moons, because there is insufficient evidence and theory to speculate what moons might be habitable on account of their proximity to a planet.

The habitable zone is not to be confused with the planetary habitability. While planetary habitability deals solely with the planetary conditions required to maintain carbon-based life, the habitable zone deals with the stellar conditions required to maintain carbon-based life, and these two factors are not meant to be interchanged.

Life is most likely to form within the circumstellar habitable zone (CHZ) within a solar system, and the galactic habitable zone (GHZ) of the larger galaxy (though research on the latter point remains in its infancy). The HZ may also be referred to as the "life zone", "Comfort Zone", "Green Belt" or "Goldilocks Zone"[2].

A "Goldilocks planet" is a planet that falls within a star's habitable zone, and the name is often specifically used for planets close to the size of Earth.[3][4] The name comes from the story of Goldilocks and the Three Bears, in which a little girl chooses from sets of three items, ignoring the ones that are too extreme (large or small, hot or cold, etc.), and settling on the one in the middle, which is "just right". Likewise, a planet following this Goldilocks Principle is one that is neither too close nor too far from a star to rule out liquid water on its surface and thus life (as humans understand it) on the planet. However, planets within a habitable zone that are unlikely to host life (e.g., gas giants) may also be called Goldilocks planets. The best example of a Goldilocks planet is the Earth itself.

http://en.wikipedia.org/wiki/Habitable_zone

My apologies for the lack of audio in this video. The green zone is the habitable zone around each star.
http://www.youtube.com/watch?v=j7XJT0N_X2U

it the optimum area for finding life but yes, there is always the possibility that we'll eventually find it somewhere we never thought