The answer to this question is going to be very different for people who have different backgrounds and are in different life situations. I will discuss sociological characteristics in general and try to help you understand what sociological characteristics you have that might make you who you are.
Sociological characteristics are, essentially, what groups you belong to. Sociology is mainly interested in knowing about the connection between group status and individual life. For example, then, many people would likely say that their income level helps to make them who they are. Others would say that it is how much education they have. Of course, a person’s sex and sexual orientation help to make them who they are. For many people, particularly members of racial or ethnic minorities, race and national origin are important. For many people, membership in a particular church (or lack thereof) is important. For many people, their age group is important, for others, it is the kind of job that they have. There are differences that come from living in an urban area or a rural area. You can be affected by whether you grew up in a household with both of your biological parents. All of these things are sociological characteristics.
Thus, what this question is asking you to do is to identify the groups that you belong to and which are important in making you who you are. Not all of the attributes that I mention in the previous paragraph will apply to you and there may be others that you will feel are important.