The hosts file in Mac OS is used to manage which IP address a domain will resolve. This can be used to load a website that is hosted online but not live by instructing your computer to load the specific IP address. This can be managed in terminal using these commands:
Open The Hosts File
sudo nano /etc/hosts
Modify the Hosts File
Add any domain/IP address combinations that you would like to manage at the end of the file. Save and close the file using the shortcut control+z.