A MOFF file is a data file used by Sony PlayMemories, a program used to manage and edit videos and images. It contains metadata about images or video referenced by PlayMemories to organize them. MOFF files may also contain GPS data recorded by an Actioncam camera (with a GPS function) that indicates where the video was captured.
MOFF files are typically created by PlayMemories to index images and videos that are played or to store GPS data from an Actioncam that was previously stored in the camera's memory. MOFF files that store Actioncam GPS data are generated when importing .MP4 files on the camera to the PlayMemories program.
PlayMemories was released in 2012 as a replacement for the Picture Motion Browser (PMB). In PMB, MOFF files were used for storing an index of recorded analysis data for Sony video. The MOFF files were typically accompanied by .MODD files to analyze a movie stored in an .M2TS file.
Since MOFF files do not contain actual video data, you can delete MOFF files and still view the image or video associated with them. However, the GPS or analysis data will not be available for the associated video or image.
NOTE: MOFF files that contain GPS data can be converted into more popular formats, such as .KML or .GPX, using GPSBabel.