Sociology is a field of study that attempts to explain how society and the groups a person belongs to affect the ways in which people behave. This is as opposed to psychology, for example, which looks at people simply as individuals.
A functionalist looks at various parts of society as parts of a body. It argues that all the parts of a society get to be that way because they serve an important function.
A conflict perspective says societal institutions get to be that way by conflict -- they are basically imposed by the elites through conflict.
Interactionists are more like psychologists, saying that society is made up of the interactions of individuals.
Sociology looks at the relationships that develops between people and their environments and their interaction with others. Sociology, like anthropology, looks at cultural customs and how relationships are affected and modified based on the understanding or misunderstanding between cultures.
Sociology also addresses social mores, how they develop, and the behaviors that emerge as a person or society responds in compliance with the mores or does not comply with the mores.
The other editor did a good job explaining the three concepts.