Rebuying is when you buy items that have already been used, but are still useful. What is the need in purchasing something brand new, when you can get it for a cheaper price, and it does not have to go to a landfill.
Also, through buying heavily packaged foods, you reduce in the waste the comes from them. The wrappers are not recyclable, and they are not good for the environment. Plus, the foods not wrapped heavily, are sometimes more healthy for your body.