How many types of academic services are available online?

I am a student and I am well aware of the trend of buying academic services from online platforms. The academic service of which I am most fond is the academic writing service. I often hire professional writers to Do My Assignment for me and get exceptional grades. Besides that; I know about class-taking service providers. So; I was just wondering if there are any other such online sites offering other such forms of academic services that I am not aware of as yet. Can someone enlighten me?