The phrase isn't a feature of a program or service, but rather a specific file naming convention used by piracy websites .
: This refers to the source website, World4uFree , a well-known platform for downloading movies and TV shows illegally. The "app" suffix often indicates the file was optimized for mobile viewing or uploaded via their specific application. world4ufree-app-finaldestination-720p-mkv
: The file extension ( Matroska Video ). This is a popular "container" format because it can hold multiple subtitle tracks and audio streams in one file. The phrase isn't a feature of a program