To recap: CD Projekt RED's RPG series The Witcher is based on Andrzej Sapkowski's short stories and novels. The Witcher Adventure Game is a monster-hunting board game adaptation made by CDPR with Fantasy Flight Games, which was also being made into a virtual board game by Can Explode. Both cardboard and cyberspace versions launched yesterday, so you can see how a video game interprets how a board game interprets how a video game interprets the adventures of a mutant monster-hunter and pals romping across a fantasy world getting into scrapes.
Playing as monster-hunter Geralt, bard Dandelion, sorcerer Triss, or warrior Yarpen, folks roam around the world completing quests. You might be killing monsters, engaging in diplomacy, charming folks, or otherwise getting involved in other people's business. You know: quests. All of this is represented by, and resolved with, cards, dice, counters, and tokens. It's got online multiplayer and local hotseat play, as well as AI if you fancy it.
As for how it all actually plays, well! It's tricky. I can say "This video game is an RPG with turn-based combat" and you'll broadly get it, or "It's a first-person shooter." Board games are somewhat beyond my expertise. Fantasy Flight have put together an explanation in five parts - count 'em: 1, 2, 3, 4, 5 -and you can see what the lot at BoardGameGeek make of it.
I am, by the way, delighted by the 'As Seen On TV' commercial-style voiceover in this trailer: