Eye candy is something that stimulates the visual senses into an almost visual overload. Although it applies to anything visual, it is usually used to describe movies, or people.
Note that although scenes like golden fields blowing in the wind, or a sunset over a white sand beach, are both serenely beautiful, they are not necessarily eye candy.
And like everything else, eye candy is energy. To illustrate, let us take the best example for movie eye candy, and that's Speed Racer, directed by the Wachowski brothers.

Human eye candy is slightly different, as it is the beauty of the person's face as a three-dimensional construction that makes it eye candy. And the human eye is likewise drawn to it, because it is unfamiliar. It is energy configured in a beautiful way, like the Aurora Borealis (which I have not yet personally laid eyes on).
That is the so-called science of eye candy.