At first I thought that you were looking for 'demographic' (which means basically the same as 'audience' in this context), but this doesn't cover the the 'articles about students or about employees or about the community' part of your question.
Since you want a word to describe what the content is about, the best word would be 'topic', as it describes what a publication is about in the same way 'audience' describes who the publication is for (was aimed at). Since it is about the 'about', 'topic' can be on "people" without a problem.
From the dictionary: 'the subject or theme of a discourse or of one of its parts'.
TopicsTopic:
- Students
- Employees
- Community/ties
You can then define subtopics if you wish, such as 'What's it like being a student', 'Student Housing', 'Student Loans', etc.