The easiest way to redeem your points is to head to Microsoft's Account website here and sign in with the same account you use on your Xbox and Windows 10 PC.
You can then spend these points on a range of rewards, including contest entries, Xbox Live and Game Pass subscriptions, charitable donations, and even cold hard cash.
Microsoft Rewards is a program that rewards you with points for, well, doing basically anything within the Microsoft ecosystem.
These are actually just plain old Microsoft Rewards points with an Xbox Game Pass twist.
You can earn Microsoft Rewards points for doing those Game Pass quests, but also searching on Bing, performing surveys on the website, and much more.