Organisms are present at various levels ranging from cellular level to biosphere level. Each level contains many smaller levels that interact with each other.
Community is defined as the various populations that occupy a given geographical area at a given point of time. At community level, a biologist may study the interactions between the various components of community. This may include various inter-population and intra-population interactions. Inter population refers to the interaction within the population, where as intra population interaction refers to the interactions between the populations.