[Update #2]: CD Projekt Red will be drastically slowing down development on Gwent: The Witcher Card Game in 2023 and beyond.
[Update]: CDPR is working on a new singleplayer-focused card game adventure based on Gwent - project Golden Nekker.
While the card game Gwent has been around since The Witcher 3, it has gone through some rather massive changes ever since it went standalone. So even though it may share the same name and core mechanics, the Gwent of today is a far more expansive and balanced card game than The Witcher 3's mini-game.
If you're wondering just how different it truly is, this would be a pretty good time to find out as Gwent has now finally made its way to Steam. Much like the other platforms, including the main GOG one, the newly launched Steam version is free-to-play with a rather unobtrusive monetization system.
You can get a small glimpse of what Gwent looks like in gameplay terms through the freshly posted Steam launch trailer. Have a peek:
Should you find yourself enjoying Gwent, you might also want to check out the standalone Thronebreaker RPG. It contains all of the same mechanics and ideas as Gwent, just wrapped into an actual story-focused RPG with plenty of choices to make and interesting characters to mess around with. Thronebreaker will be on a 50% discount until June 1st, so if you find yourself itching for more card-based action, it's well worth a closer look.
Have fun!