what exactly Tox is?
Tox (https://tox.im) is a free, open-source, peer-2-peer (decentralized) messenger, built around bits of DHT (BitTorrent) technology. it's designed to be as secure as possible, and the main purpose of whole project is to build open-source, spyware-free alternative to Skype.

who the hell thinks that's a good idea?
a bunch of guys on 4chan did one day, so they decided to give it a whirl.

i've heard that developers' team was disbanded, is that true?
for a quite some time, Tox was developed by a Tox Foundation, a 501(c)3 tax-exempt nonprofit organization in the USA; that is no longer the case, though -- recently (Jul 2015) it was discovered that Sean Qureshi, Tox Foundation head and sole board member, used all of TF' money for an education loan without other developer's and maintainers permission. eventually, all active project developers had to disaccociate themselves from TF, and now (since Aug 2015) they're working independently, as they did in the very beginning.

oh snap! was tox' source code compromised because of this snafu?
no. project's heart, libtoxcore library is and always was developed mainly by one person known as irungentoo, and all of its source was stored on github repo, which never was under Tox Foundation' control. nevertheless, since some of Tox-related resources (project website, toxme.se name repository and some others) were maintained by Qureshi, and he's single-handedly controls them and their domains, it is highly recommended not to use these services anymore.

tl;dr, can you please explain wtf Tox it is, in one sentence?
Tox is a chat tool which purposed to be secure as hell, but easy enough to use for your grandma

okay, but why should I use it?
the entire principle "I've got nothing to hide from {three-letter-agency-of-your-choice}" is rotten by design. they shouldn't listen to your calls or read your mail just because it's none of their business, end of story.

but i'm no terrorist, should i use it anyway? i've got nothing to hide!
yes, you should. learn to respect yourself and your right to have your own secrets. even if all they're about is how many cats you've got.

what can i do with Tox?
send and recieve text messages, participate in video- and audio-chats (not implemented by all existing clients yet -- but it'll be), send & recieve files, and more.

where can i use Tox?
there's clients for literally every platform alive: Windows, Linux, Android, MacOS and iOS. there's also handful of plugins for existing messengers, like Pidgin or Miranda NG. unfortunately, there's no implementation for Windows Phone yet.

fair enough, i'd like to try it. where to start?
https://tox.chat. and don't forget to tell your friends about it.