Autotrophs are organisms capable of manufacturing their own food. They usually do this from simple, energy poor, inorganic compounds; either through photosynthesis or chemosynthesis. Photosynthesis is carried out by chlorophyll/pigment containing organisms e.g algae, crymtomgams and higher plants, in light. Chemosynthesis is carried out by some bacteria, e.g sulphur bacteria and nitrogen fixing bacteria
Heterotrophs are organisms which rely on already formed food for nutrition, they breakdown complex food molecules (organic) into simpler ones. They are either parasites or saprophytes; parasites depend on living host tissues for survival e.g some fungi, bacteria, viruses, worms, parasitic plants, etc. Saprophytes depend on dead, decaying organic matter, e.g fungi like mushroom, toadstool, mucor, etc.