For the longest time ever, PCs and keyboards have come with media keys on them. These keys provide shortcuts for users to control their media, such as pausing/playing a song, skipping a track, and so on. However the only downside is that for the most part, they only worked with apps and not websites.
This means that if you’re watching a YouTube video, you will need to go to the video to pause it instead of using the media key. However the good news is that Google has recently updated its Chrome browser where it will now support your PC’s media keys. This means that while you watch videos on the web, you will be able to control its playback using those media keys if you choose to.
This will work even if the browser is in the background, like if you have a YouTube music playlist that is playing, you can use the media keys to control its playback without having to bring the browser to the foreground. However a downside as noted by Engadget is that if you do keep other media apps open, like VLC, iTunes, and so on, it could interfere with the controls so do keep that in mind if you plan on taking advantage of the feature.