What is the use of host files ? where they are located?

You may follow steps in this artical:

http://www.howtogeek.com/howto/27350/beginner-geek-how-to-edit-your-hosts-file/

id u do'nt have DNS or u want to use an IP for specific machine u can use it ,

its place is

%systemroot%/System\\drivers\\etc

it is located in %systemroot%\\System32\\drivers\\etc

it is used for looking into hostname entry order is1 before dns server

IT IS A TEXT FILE WHICH CONTAIN AT LEAST IP ADDRESS SEPERATED BY ONE SPACE AND DOMAIN NAME..IT IS USED IN THE CASE  WITHOUT DNS..

IT IS ALSO USED FOR

*TO SPEED UP THE BROWSING SPEED

*NETWORK TESTING

*TO BLOCK SPYWARES 

it is a local small DNS DB to store spasific IP with it names

c:\\windows\\system32\\drivers\\etc

HOSTS Filethis is a text file that statically maps hostnames to IP addresses.

This file is Located in c:\\windows\\system32\\drivers\\etc for standard Windows Server2012 R2 installations 

it can be used as an entry-level alternative to a DNS server for name resolution in Small environments.

located : c:\\windows\\system32\\drivers\\etc

this is DNS for local PC it will lookup first to it local file then it will lookup to the DNS server is present adn the below is the order or the sequence will follow

Host name resolution generally uses the following sequence:

1. The client checks to see if the name queried is its own.
2. The client then searches a local Hosts file, a list of IP address and names stored on the local computer.NOTE: The Hosts file location depends on the operating system: Windows NT %Systemroot%\\System32\\Drivers\\Etc Windows95 <drive>\\<Windows folder> Windows for Workgroups <drive>\\<Windows folder> Windows3.1 <drive>\\<Windows folder> MS-Client3.0 <Boot volume>\\Net Lan Manager2.2c Client <Boot volume>\\Net Where %Systemroot% is the folder in which Windows NT is installed, <drive> is the drive on which the OS is installed, and <boot volume> refers to a boot floppy disk or drive C.A sample hosts file, Hosts.sam, is installed with the TCP/IP protocol showing the proper format.
3. Domain Name System (DNS) servers are queried.
4. If the name is still not resolved, NetBIOS name resolution sequence is used as a backup. This order can be changed by configuring the NetBIOS node type of the client.