IIS stands for Internet Information Services. In the past, Internet Information Service was known as Internet Information Server. It is basically an extendible web server, formed by Microsoft for using it with the Windows NT family.
Internet Information Service helps in the maintenance of HTTPS, FTP, HTTP, FTPS, NNTP and SMTP. Since the coming of Windows NT 4.0, it has always been an essential part of the Windows NT family. Still it is not present in some of the editions like Windows XP Home Edition. There is no way you can turn it on by default, if you have windows installed. The Internet Information Service Manager can be accessed through the Administrative Tools in the control panel or through Microsoft management console.
As per the survey conducted on 13th of February 2014 by the Netcraft, IIS has taken on the second position in the ranking for the most popular or famous web servers in the world. Apache HTTP holds the first position with 32.80% of market shares in hand.