The hosts file is a vital file built into Windows. Its purpose is to convert IP addresses to host names, much like DNS would. This can be useful in pointing an individual PC to a specific server where DNS may point it elsewhere.
For example, normally example.com would point to 126.96.36.199, however you may want it to point to 10.87.1.5 on only one PC. You could use a host file entry to point this one PC to 10.87.1.5.
This guide will show you how you can easily edit the host file on your Windows machine