Up until now, if you saw a YouTube video you liked embedded in a website, you had to click through the video to YouTube's page in order to subscribe to that channel. Now, YouTube is making it a little easier for viewers to see the videos they want (and for channel operators to grab those subscribers). Going forward, YouTube embeds will feature a "Subscribe" button.
You can see the subscribe button in action in the video below, which is our Samsung Galaxy Book 2 hands-on. If you hover over the Engadget logo on the top left, an option to subscribe to our channel will appear. The feature was first spotted by 9to5Google.