The file extension AEP is used by the video compositing and animation software Adobe After Effects for project files. In addition to references to videos, audio files and images, AEP files also contain cut and timeline information and effects settings.
Usually, the paths to the media files are also saved, so that they are only found if they are in the original directory. But you can also load AEP files and specify new locations for missing files.
It should be noted that AEP files are usually not backwards compatible, so with the CS4 version, for example, no CS3 compatible AEP files can be created.