Files of the .msi type are Windows Installer packages, designed as a compact database to install software onto the computer, often on demand. It contains information as to where files need to go, what files need to be removed and what has been changed with each portion of the installation.
The .msi file type is an installation standard by Microsoft that gives software developers a framework for deploying software on to the Windows operating system. A Windows Installer package keeps a persistent size, without having to unpack data and is often used for deploying software bundles across a network. Using the .msi framework keeps the database of installed components streamlined, making it easier to undo a mistake done during the installation of the package.