An OBB file is a type of file used by Android apps to store large amounts of data, such as graphics, audio files, and other game assets. In the case of Dream League Soccer, the OBB file contains essential game data, including team logos, player images, and stadium graphics. The OBB file is used to supplement the game's APK (Android Package File) and provides a way for developers to distribute large amounts of data without having to include it in the APK itself.