Plant cells have pigmented bodies called plastids which are of three types
Chloroplasts
Chromoplasts
Leukoplasts

Chloroplasts are meant for photosynthesis where it combine carbon dioxide and water to form glucose.
Chromoplasts are usually found in parts of the plant where we see colors like petals or vegetables.
Leukoplasts are usually found in those parts of the plant which are concerned with food storage.

Thus
Its a part of cell.
Found only in plants.
Concerned with preparation of foood through photosynthesis.