The category "Personal Communications" is used in situations where you are taking information from a source such as an email thread or an interview you conducted with someone else. In this case the work isn't published anywhere, someone else couldn't find and read the full interview or email on their own.
Sometimes you may find interviews with people in journals, magazines, newspapers, websites, etc. In those cases don't use the "Personal Communications" category. Instead, cite them according to where you found the information.
For example, an interview in a magazine would be cited like a magazine article. That way anyone reading your assignment could easily track down the interview for themselves by finding the same magazine article.