The Gear S3 is getting loads of features in a new update that Samsung is now starting to push out to device owners. The update weighs in at about 129-130MB and you should receive a notification about the update through your Samsung Gear app that you have installed on your phone, but as with any other update you can always check manually to see if the update is available. If it is, then you should see a fairly long list of changes to the Gear S3 as Samsung details all of the new stuff there will be to look forward to in a pretty decent sized changelog.
This new update applies to both the Gear S3 Frontier and the Gear S3 Classic, so no matter which version of the Gear S3 you have you will end up with the update. That being said, although Samsung has started pushing the update out today it doesn't necessarily mean all users will see the update today. As for what's new, Samsung has added in new partner apps that you can download from the Galaxy Apps Store, like Spotify and BMW Connected, and if you're so inclined you can even browse the internet on your watch via the Samsung Internet app that's now available for it.
In addition to some new apps that can be picked up from the Galaxy Apps Store, Samsung has also added in plenty of improvements to features of the watch as well as existing apps. For instance, they've now made it possible to add date and music details to some of the watch faces similar to the way that some Android Wear watch faces in 2.0 can have widgets attached to them. If you use S Voice on the Gear S3 to set reminders, you can now use it to add dates and times to those reminders, and they've added in the Find My Gear feature which lets you display your contact information on the screen of the Gear S3 so that if it gets lost someone would know who to return it to. You can now also set the stopwatch time all the way up to 3 hours, and there are quite a few more changes too. The update isn't too large so when it does show up for your device, it shouldn't take too long to download and install it, just make sure your watch is connected.