OSS came first, then got replaced by ALSA after it became proprietary.
PulseAudio is a userspace audio server to which programs connect. It manages audio settings per app, then sends everything to ALSA. JACK is the same but with a focus on low latency.
PipeWire is a modern drop-in replacement for both, and also has support for video on Wayland.
Real talk, though: why has Linux taken at least five tries (OSS, ALSA, JACK, PulseAudio, PipeWire) to get audio right?!
OSS came first, then got replaced by ALSA after it became proprietary.
PulseAudio is a userspace audio server to which programs connect. It manages audio settings per app, then sends everything to ALSA. JACK is the same but with a focus on low latency.
PipeWire is a modern drop-in replacement for both, and also has support for video on Wayland.
And then there’s also sndio, ported from OpenBSD. This does basically the same thing as OSS/ALSA.
That’s the thing about open source. Someone always thinks they can do better
Relevant
I’m still waiting for the latency to be viable for playing guitar with an audio interface.