Photosynthesis takes place inside of chloroplasts, which are inside plant cells. Photosynthesis is the process by which plants turn sunlight into energy.
Just like animals, plants need energy to carry out their basic functions of survival. They produce their energy by combining carbon dioxide, nutrients, water and sunlight. Thylakoids are disc-like shapes that trap the sunlight for this purpose, which are stacked inside chloroplasts. The thylakoids contain chlorophyll, which is what gives plants their green color.
Generally, the plant uses these thylakoids to convert sunlight and carbon dioxide to glucose, a sugar that is usable by the plant. Plants release oxygen during the photosynthesis process, which is the opposite of what animals do. Humans, for instance, breathe in oxygen and breathe out carbon dioxide.