Delivery Optimization is a Windows 10 feature first released with the Windows 10 November 1511 update, and it allows you to download Windows 10 updates from the internet to one PC, and then update other Windows 10 machines from there.
With Windows 10 Insider build 14915, released this morning, Insiders can now get Insider builds, beginning with todays 14915 update, through Delivery Optimization.
Delivery Optimization is on by default, and if you have it turned on for multiple devices on your local network, or have it set to use over the internet, you'll be able to take advantage of the feature for faster, and potentially less costly downloads (especially if you're on a metered network). Here's more from today's blog post on 14915:
In addition to downloading apps, app updates and OS updates from the Windows Update servers, Delivery Optimization will look for nearby PCs on your local network or on the Internet that have Delivery Optimization enabled and find the app or OS update you need that may be even closer to your PC. Rather than downloading an entire file from one machine, Delivery Optimization breaks the download into small pieces and uses what is assessed as the fastest, most reliable source for each piece of the file. Delivery Optimization is also mindful of local disk usage, use of cellular networks, battery life, and other network activity. It is also integrated with and builds on the existing security measures in Windows Update and Windows Store to check the authenticity of each file downloaded from other PCs. Particularly for PCs with challenging network conditions, this is designed to provide a better and more reliable download experience.
To check if Delivery Optimization is set for your PCs, go to Settings > Update & security > Windows Update > Advanced options and choosing “Choose how updates are delivered.”