As the name suggests, fake virus services are services that claim to remove viruses from your computer, but in reality, they do nothing. These services are often advertised by pop-ups or other online ads, and they usually charge a fee for their "services." Fake virus services are a scam, and you should never use them. If you're worried that your computer has a virus, you can use a free virus scanner such as Microsoft Safety Scanner or Malwarebytes Anti-Malware to check for and remove viruses.
There are services that will create a fake virus for you. This can be useful for testing your anti-virus software or for pranking your friends. Be careful though, as some of these services may be scams.
There are a number of ways to make fake virus services. The most common is to use a free online service that allows you to create a fake virus. Another way is to use a virus creation program that you can download for free. There are also a number of websites that offer fake virus services for a fee.