What Are AAX vs AU vs CLAP vs VST vs AU Audio Plugins?

AAX

AAX, Avid Audio Extension, is a plug-in format developed by Avid Technology, makers of video editing software Avid.

AU

AU, Audio Units, is a plug-in format developed by Apple for macOS and iOS. It is closed source.

CLAP

CLAP stands for Clever Audio Plug-in. It's an open source alternative to all of the other plug-in formats which are proprietary.

It was developed by u-he and Bitwig.

CLAP has support for true MIDI 2.0, great multi-core CPU performance, and an open MIT licensing

VST, VST3

VST, Virtual Studio Technology, is a plug-in format developed by Steinberg. It was released in 1996, was superseded by VST 3 in 2008, and is closed source.