Yeah, you can select "edge" for some resources (API Gateway and Lambda are two that come to mind) which just means it's located in all regions plus some additional "edge" infrastructure that isn't available as a region. AWS puts some restrictions on edge resources since there isn't enough capacity or full-region functionality.

Usually you pick this for stuff that is CDN oriented and front a regional service with that.

Exactly, why did it failed yesterday then? If supposedly just us-west-2 was down :(

My guess is if you saw an outage with edge, it was because you were being routed by us-west-2