Specifically, it's giving out Premiere Bundles. Which contain a white Stadia controller, a Chromecast Ultra so you can play on your TV, and a 30-day subscription to Stadia Pro.
All things considered, this is a pretty good deal if you already subscribe to YouTube Premium. Even if you plan to sign up just to get this bundle for free, you could easily keep YouTube Premium for its trial period, receive your free bundle, and then cancel the subscription.
Or you could just keep it. Either way you end up on top here. But there is a caveat or two.
The Stadia YouTube Premium deal isn't available everywhere
Google may eventually hand this promotional deal out to every country where Stadia can currently be used. As of right now though, that's not the case. You can only snag the promotion in two countries.
That includes the US, and the UK. As noted this may eventually extend to other countries but at the moment you need to be living in one of these two regions. That being said it's possible that Google is piloting the promotion to see how it goes before deciding to offer it elsewhere.
To claim this offer, eligible subscribers will need to wait until Google sends out an email with the redemption code. You need to then claim the offer with that code at the Google Store. Lastly, you need to do so by December 31 of this year at 11:59PM PST. So you won't have a super long time grab it.
It's possible that not all Premium subscribers are eligible
Though all YouTube Premium subscribers should be eligible for this promotion, you might want to be prepared for the fact that you're not.
You can check to see if you're eligible at this link. Be sure though that you're logged into the Google account that subscribes to YouTube Premium. That is if you have more than one Google account.
If you're not logged into the right one, there is a button in the top right corner that allows you to switch accounts. So being logged in with the correct one from the start is just about saving yourself some time.
Another thing to keep in mind is that this is a bundle which normally costs $99. So if you already have a Stadia membership and you subscribe to YouTube Premium, you may as well claim the offer if you can.
An earlier version of this post incorrectly stated that the free Premiere Bundle as part of this promotion came with a 90-day Pro subscription.
The subscription is actually for 30 days. The post has been updated to reflect these details.