Recently, Microsoft released Windows 10 for PCs Insider Preview build 14279 to the Fast ring. The build contains new features, fixes a few things, breaks a few things, and notes a few existing things.
While there have been a number of builds that are part of the Redstone update, this is only the third that contains actual new features.
Typically, while Microsoft is still adding features to an update through Insider Preview builds, it's safe to assume that it's not stable enough to be used as a daily driver (especially Fast ring builds). Once the update is feature complete, then the firm begins to refine it. Of course, Microsoft will likely be announcing even more features for Redstone at Build.
Currently, not a whole lot is known about the Redstone update for sure. Features that have been added are minor, such as history dropdown menus in Edge or reminders that can be set later in Cortana. One feature that was added in build 14267 was that users could send photos through Skype in the Messaging + Skype app; however, that feature ended up rolling out to non-Insiders as well.
Rumors are that Redstone will bring back OneDrive placeholders, bring calling and text messaging to PCs (even if the user is using a non-Windows phone), windowed apps in Continuum for phones, UWP apps on Xbox One, browser extensions in Edge, and more. Of course, these are exactly the types of things that the firm would wait until Build to talk about.
While there's clearly a lot more to come at the end of the month, there's still a lot to talk about right now. Here's our hands-on video with Windows 10 for PCs build 14279: