DAT file is a file format written to save sounds, midi, wave, pallets, images, and levels. In short, this file format contains vital information for specific software, and the data is usually in either binary or plain text. In rare cases, DAT files may include a video file. DAT files are opened using text editors like Notepad++ and TextEdit.
FLV (Flash Video) is a video container format developed by Adobe Systems and comes with a .flv filename format. FLV is primarily used to stream audio, video, and text data such as subtitles. It supports MPEG-4 Part 10 (H.264) video codec and AAC sound.
RealPlayer, Apple QuicTime Player
VLC Media Player