Quote:Tox is a free as in freedom peer to peer, end-to-end encrypted, distributed, multimedia messenger.

It consists of a core, and a number of clients.

Tox is just the core, the part of the program which handles the messages and encryption, for instance. But it can only function in the context of a complete instant messaging program. All the fancy user interfaces you see all over the place, are the clients. The client is a separate program which utilizes the core, providing a convenient way to use the program. So when you use Tox, you are in fact using one of the clients. The most clients are graphical clients, in other words, you will make use of all kinds of graphical elements which are part of the client. You usually won't get to see the core (unless you look into the source on GitHub). There are various clients available which each have a different name, are independent from each-other, in various programming languages.

For example, file sharing and A/V (audio and video) are handled by the core, but the (for example!) pop-ups, per-person volume sliding bars, friends list etc, buttons etc. are all handled by the client.

When you are referring to the Tox protocol or in general, you are talking about Tox.

When you are referring to the Tox program itself, you are talking about the Tox core, usually written as toxcore (see the Git)

When you are referring to one of the clients, you should mention the name of the client instead of 'Tox' or 'toxcore', such as Toxic or qTox (see Client)

Quote: Which encryption algorithms does Tox employ?

Tox uses the encryption algorithms present in the NaCl crypto library.

“<irungentoo> (…) curve25519 for the key exchange, xsalsa20 for the encryption and poly1305 for the MAC”

More info: https://github.com/irungentoo/toxcore/blob/master/docs/updates/Crypto.md