It is a natural and adaptive social process to classify people into groups. however, because we inhabit one of these groups, we tend to favor our ingroup. what concept explains this tendency to put people, including yourself, into groups?

It is called, Social Categorization.

Explanation:

Social Categorization is the putting of people including yourself into a group based upon some factor. There are two types of categories, In group category and out group category. In group category is the one in which you include your self too. Social Categorization can be done on the basis of many factors like, race, ethnicity, religion, social class, power, education, etc. There could be any category in which the people may be differentiated. This is called Social Categorization.

is answer is two