What are the main interspecific population regulatory interactions? How do they work?

The main inter-specific population regulatory interactions are:

Predator-prey relationship Mutualism Commensalism

Predator-prey relationship:

Predators can actually make the population of a prey stable by feeding on organisms which are weak or old in a prey population.

Mutualism:

Mutualism can be described as a type of interaction in which both organisms benefit from each other.

Commensalism:

Commensalism is a type of interaction in which one organism benefits from the other organism while the other organism neither gains benefit nor is harmed.