I need a little help its a confusing question
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Light refracts because when it goes from a less dense to a more dense medium its velocity slows down. So, consider a beam of light entering a block of glass at some angle. The beam has a certain width. As the beam makes contact with the edge of the glass, one part of the beam enters the glass first. When it does, it starts to slow down. But the rest of the beam is still in the air, and is moving faster. Then the next part of the beam enters the glass and slows down, but the rest of the beam is still in the air. This continues until the whole of the beam is in the glass. The overall effect is that the beam bends towards the normal at the point of incidence. That is what we call refraction.
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The explanation depends on what level you are and how much maths you have. Look at the links for starters.
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Can you be more specific?