Application.manifest

Windows component manifest Reference

A .manifest file contains an XML description of a software component on Windows. The manifest gives the identity, the version, the files, and the dependencies of the component. Windows uses manifests for side-by-side assemblies and for the servicing of system components. An application manifest can also declare settings, for example the requested execution level. The file is plain text.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.