A WLMP file is a project file created by Windows Live Movie Maker, a video editing software developed by Microsoft. It is crucial to understand that a WLMP file is not a video file itself, but rather an XML-based file that stores all the instructions and references needed to create a video. This includes information about the arrangement of video clips, audio tracks, images, applied effects, transitions, titles, and credits on a timeline. When you save a project in Windows Live Movie Maker, it creates a .wlmp file. To open and work on this project, you must have Windows Live Movie Maker installed, and all the original media files (videos, photos, audio) referenced within the WLMP file must be present and accessible in their original locations. If any source media files are moved or deleted, the WLMP project will show missing file errors. To share or view the final video on other devices or platforms, the WLMP project must be exported or 'published' into a standard video format like WMV (Windows Media Video) or MP4. Windows Live Movie Maker was part of the Windows Essentials suite and has since been discontinued by Microsoft, making WLMP a legacy format, though still usable on systems with the software installed.