MP4 (MPEG-4 Part 14) is a video container format based on QuickTime MOV. But unlike MOV, it adds support for other MPEG features. MP4 supports video (MPEG-4 Part 2 and MPEG-4 Part 10/H.264), audio (MP3, AAC, SLS, TTSI, and ALAC), and subtitles (MPEG-4 timed text). It’s this codec combination that gives MP4 its flexibility.
Windows Media Player VLC Media Player, Apple QuickTime Player 5KPLayer
AAX (Atom Asset Exchange) is an audio file format for storing sound-based products from Audible Incorporated. Typically, AAX files are DRM protected, although they can be transcoded to other common formats such as MP3 using a licensed program like Wondershare UniConverter.