What is an organism that is able to make its own food?

The answer is autotroph.

The word autotroph is made of two greek words - autos meaning self and trophe meaning nourishing. So, autotroph would be a self-feeding organism. Autotrophs, such as plants, some bacteria and fungi, are organisms able to make their own food. They do that in the process of photosynthesis or chemosynthesis. Photosynthesis is a process in which plants use Sunlight and thanks to the pigments in the leaves that are able to absorb Sunlight, they produce sugar (a food) and oxygen from carbon dioxide and the water. Chemosynthesis is a process in which some bacteria produce sugar (which is a food), similarly to photosynthetic process. But, this process is preferable when there is no light and the environment is rich in sulfide or methane.