It is an algorithm that allows you to balance requests based on latency. Think of it as CDN.
How it works
Imagine you have load balancers in the US and Europe and you attach latency based routing record for each load balancer. When someone visits from Europe, a DNS refers to its data about latency and checks which one is the best for that particular user.
Transclude of Latency-Based-Routing.excalidraw