Rainbow Six Siege has recently been updated with Operation Velvet Shell, which among the variety of bug fixes and UI tweaks has also added two new Operators, as well as a free map by the name of Coastline. The two new Operators, Mira and Jackal, are currently exclusive to Season Pass owners, but don't worry, you'll be able to unlock them with Renown or R6 Credits in less than a week.
If you're wondering what the new map looks like, and more importantly, what the two new Operators bring to the table, here's the recently posted preview video. There isn't much pure gameplay in there, but it should still get the point across. Anyway, here's the video:
Besides the newly added Operators and map there is also a whole bunch of UI updates, bug fixes, and even a rather significant balance change. Since purely visual changes are a bit hard to explain through text alone I would suggest you visit the official website if you're looking for all of the details.
And finally, if you're wondering about Rainbow Six Siege and its future, allow me to just say that Ubisoft has recently announced a second Season Pass. Long story short, expect to see eight new Operators throughout 2017, as well as a constant influx of major updates and balance changes. Whether the Season Pass is worth it or not, that I'll leave for you to decide, but its still good to hear that Ubisoft remains committed to Rainbow Six Siege.