Zcash is the third iteration of an extension to the Bitcoin protocol that provides true untraceability, i.e. fully anonymous transactions. It is arguably the first serious attempt to establish this extension, in the form of its own blockchain, beyond the form of an academic proposal. The talk provides an introduction to the magic that makes it work.
This Talk was translated into multiple languages. The files available for download contain all languages as separate audio-tracks. Most desktop video players allow you to choose between them.
Please look for "audio tracks" in your desktop video player.