In short:
SLab is an application which turns your computer into a complete home studio.

More verbose: (From slab.history)
SLab is a multitrack harddisk recording application, a set of tools to record music to disk on a PC platform (running Unix of course). The application is software only, it just requires a reasonable PC with a soundcard. There are some limitations on soundcard support, and obviously some limits on track counts based on CPU/disk performance.

The name is pronounced either "slab" as a single word, or "ess-lab", whichever you prefer. I would have given it some groovy name, but most of the names I would like are already in use! "Yet another audio recording tool" would perhaps be a good alternative, since there are many available.

SLab consists of a mixing desk, tape deck, wave editor, and a few other auxilliary tools including digital effects processing.