Windows 10 is using your network bandwidth to share updates with other Windows 10 users across the Internet. Windows Update Delivery Optimization (WUDO) is enabled by default in Windows 10 Home and Pro edition. WUDO works a lot like torrents work to deliver software updates faster to others. Microsoft said the feature “helps people get updates more quickly if they have a limited or unreliable internet connection” Users can disable the feature, but enabling it by default without the knowledge of users is probably not at all a great idea.
Source: https://thehackernews.com/2015/08/windows-10-update.html