[rvnx]

Another way to see the situation:

Internet is just a bunch of computers interconnected via tons of cables (hence the name; "inter-networked computers").

To be reachable, every equipment and computer constantly need to tell the others about their existence (to publicly announce on which network cable they can be reached at).

Facebook engineers wanted to optimise that system but accidentally broke it during the update.

As a consequence, after a few minutes, other computers didn't know on which cables they can reach Facebook.

Facebook had to call the technicians sitting in the datacenter to cancel the last change that was done (because the Facebook engineers couldn't themselves connect from the office) and everything was fine again.