IIS, which stands for Internet Information Server, is a web server software developed by Microsoft that runs on Windows operating systems. There are several synonyms for IIS including Microsoft IIS, Windows Server IIS, and ISS. All of these terms are commonly used to refer to the same web server software. IIS is frequently used to host and manage websites, web applications, and web services. It provides a variety of features and functionalities, such as support for multiple websites on a single server and integration with other Microsoft technologies like ASP.NET and SQL Server. As a popular web server software, IIS is widely used in enterprise and business environments.