What traffic goes to office.live.com ?

The Office 365 URLs are published https://docs.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide
We have accidentally blocked some of the "Required" URLs and see no adverse effects, so want to know what traffic goes to an endpoint.

How do I find out why office.live.com is on the list?  What traffic goes to office.live.com ?