There is no type of sociology that is called “basic sociology” in contrast to some other sort of sociology. Instead, “basic sociology” is really just the basic aspects of sociology as a discipline.
The basic fact about sociology is that it is the social science that studies human behavior within society. It is important to note the words “within society” here. Sociology is not very interested in the psychological processes that drive individuals. Instead, sociology is more concerned with the ways in which human beings interact with one another and how they affect the way other humans behave. Sociology is much more interested, then, in human beings as parts of groups.
Sociology largely tries to explain how societies work, why they come to be the way they are, and how they and individuals affect one another. Therefore, sociology looks at such things as the groups that people belong to. It asks why they belong to those groups and how those groups affect them. It looks at how groups are put together to form a society. For example, it asks which groups are higher up in society and which are lower and it asks how membership in these groups affects people.
In short, sociology asks questions about society and human beings and their interactions with one another. This is the basic idea of sociology. “Basic sociology,” then, is a term that simply refers to the most typical and fundamental questions that arise in sociological inquiry. This differs from applied sociology which refers to the principles of sociology employed outside a university setting to collect in-depth data for understanding of some specific facet of society for which the data can be analyzed.