AVI (Audio Video Interleave) is a digital multimedia container format developed by Microsoft in 1992 for its Video for Windows project. This file format saves both video and audio data in its container that supports synchronous audio-with-video playback. And like DVD format, AVI allows multiple audio and video streaming as well.
Apple QuickTime Player VLC Media Player Adobe Premier Pro 2020 Windows Media Player
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