Commensalism is the interaction (population interaction) between two creatures in which one is benefited but the other is neutral, i.e. neither benefited nor injured.
Commensalism can be seen in cattle egrets and livestock, birds following army ants, barnacles and whales, and so on.
Population interaction is one of the important processes that govern the organization of a community and refers to the interrelationship between the community's participants in aggregate.