The light-independent reactions of photosynthesis take place in the stroma of the chloroplasts. These are the same organelles where the light-dependent reactions of photosynthesis take place, but those happen in a different part of the chloroplast: the thylakoid membrane.
The light-independent reactions of chloroplasts are the reactions in which plants use the energy generated by the light-dependent reactions to turn water and carbon dioxide into sugar and oxygen. The light-dependent reactions of photosynthesis generate a molecule known as ATP, which stores the light energy. It is this stored energy that allows the other molecules to be broken down and reformed.