What is /etc/hosts in ubuntu?

+ We use /etc/hosts to create a host for testing purpose. 

+ We don't have a real domain name for our web server and we're not going to set one up this stage because he new internal network we're not going to go to the complexities of having DNS server or registering a real domain name but sometimes for testing purposes, I would like to give it a domain name. 

+ Instead of type ip address for testing, I'd like to type in a domain name by configing /etc/hosts.