Answer:
Predation is an interaction in which one organism kills and eats another.
This is why an organism that kills another is called a predator. Snakes for instance, are predators of rodents.
Competition is an interaction in which two organisms require the same limited resources.
When organisms require the same resources yet these resources are limited, they will have to compete amongst themselves for those resources. This is what gives rise to Natural Selection.
Cooperation is an interaction in which organisms work together to improve their survival.
Sometimes organisms will work together so that they may have better chances are surviving the environment. This is what drives humans to form complex societies.