Downloading KB3176938 will require a system restart to update your PC to 14393.105. No changelog is posted as of yet.
Right now, we see the update rolling out only for PC, but we would not be surprised if Mobile takes effect at some point. We’ll keep checking and update this post if any new information comes in about Mobile or changes.
To be clear, this is simply a cumulative update (fixes and patches) to the existing Anniversary Update branch and not Windows 10 Redstone 2. All PCs and Mobile phones will get a similar update once Microsoft signs off on testing and feedback from Insiders likely next Tuesday or the week after.