A WLMP file is a project file created by Windows Live Movie Maker, a discontinued video editing software that was part of the Windows Essentials suite. It doesn't contain the actual video and audio data; instead, it stores information about the video project, including the sequence of video clips, audio tracks, transitions, effects, titles, and other editing decisions made within the software. Think of it as a recipe for creating a video, not the ingredients themselves. To create an actual video file, the WLMP project file needs to be rendered or exported into a standard video format like MP4 or WMV. Opening a WLMP file in Windows Live Movie Maker allows you to continue editing the project or export it to a playable video file. Without the original source files (video clips, audio files, images), the WLMP file is essentially useless, as it only contains references to those files.