Apple seeded the fourth beta for iOS 11.2, just one day after releasing iOS 11.1.2 to the public. The new iOS 11.2 beta 4 has also already hit public beta testers and includes mostly bug fixes and security patches to improve the overall experience for iPhone owners.
The fourth beta does not appear to add any new features to iOS 11.2, unlike the track record for this beta's releases. Beta 3 introduced pop-up alerts for the Wi-Fi and Bluetooth buttons in Control Center, while beta 2 introduced new iPhone X live wallpapers and Apple Pay Cash.
As a whole, iOS 11.2 has many changes over iOS 11.1.2, such as adding fast wireless charging to the 2017 line of iPhones, as well as giving exclusive iPhone X, 8, and 8 Plus wallpapers to previous iPhone models.
The beta comes at a time where Apple's OS has seen its share of scandals, none more infamous than the "i" glitch, which would autocorrect the lowercase "i" to "A [?]." Apple did eventually release a patch for the glitch, but not before the Apple world blew up in frustration.
If you are running the developer or public beta, you should see the update in your Settings app.