Ubuntu supports a wide variety of sound hardware and software. Two models of sound card drivers compete for prominence in today’s market:
ALSA, the Advanced Linux Sound Architecture, which is entirely open source
OSS, the Open Sound System, which offers free and commercial drivers
Ubuntu uses ALSA because ALSA is the sound architecture for the 2.6 series, and now the 3.x series, of kernels. OSS might still be found here and there, but it is no longer in widespread use and should be considered deprecated.
ALSA supports a long list of ...