Autotrophs make their own food from inorganic material.

Most commonly, autotrophs make their own food through
photosynthesis and by using the building blocks CO₂, H₂0, N₂, and NH_3.

Chemosynthetic bacteria are an exception. 
They are autotrophs that do not use photosynthesis. 
They get their food through a reduced inorganic compound (like H₂S).

Autotrophs are sessile and move by growth.
They lack digestive organs.

Typically, autotrophs are selective in what they take in. 
This results in little waste.

Heterotrophs need at least one major nutrient from an organic source
(a hydrogen/carbon based source).

They tend to be motive or to take advantage of currents.

Heterotrophs ingest, digest, collect energy, and accumulate waste.

They are not particularly selective in what they take in,
thus they need to separate waste from the beneficial materials.