Comments about your geek card aside... ;-)
Sonos is a brand of network attached music players. Most of their products are essentially 'wifi speakers', which not only connect to your local wifi (or wired lan), but also communicate with each other when necessary to create stereo pairs or groups which all play the same thing exactly in-sync. They claim to be able to play just about all the audio on the planet, although Amazon Music seems to be a constant problem, as does SoundCloud. That said though, they really do play an awful lot of stuff extremely well.
There are some (reasonable) criticisms of the product line though. They're considered to be expensive (and more expensive than most competing products), and whilst their audio quality is generally considered to be pretty good, it could be better. Products like the 'Amp' (which has no speakers, it needs some wired speakers to be added) is only 50W, whereas pretty much any amp you could even consider being decent quality is more like 200W upwards. Also, the Amp costs more than two "Sonos 1" devices (which are, more or less, single speakers + network attachment), so it's expensive, and not as good as it really should be, given Sonos pitches itself as being somewhat 'premium'.
Technically, Sonos is pretty interesting. To work around people's crappy home wifi, Sonos has it's own mesh network which means that a Sonos device can be out of reliable range of your Wifi, but still play music just fine. The magic sauce that makes it all work is proprietary, and so you can't hack together a Sonos-compatible device on a Raspberry Pi or something. There are some 'hacks' you can do though, like turning off all wireless in devices you've wired to the lan. It's not really documented or talked about, but if you fill a rack with a load of sonos it'll probably crash your wifi (even if wired) until you turn off wifi on the devices. Devices have dual ethernet ports in a sort of hub arrangement, so you can daisychain them together if you need to.
As for John MacFarlane - honestly, I have no idea who he is. From the summary, I'd guess he's a somewhat visionary tech-savvy business guy who started a company from very little and made it into a multinational that at lot of people have heard of (granted, that doesn't appear to be you). I'm guessing his moving on suggests that Sonos's business will change in the coming months, and as is so often the case, that may not be a good thing for those of us with an existing investment.