[Radar] realtime routes visualization glossary (cloudflare#22408)

Author: digizeph

src/content/docs/radar/glossary.mdx

@@ -68,6 +68,25 @@ of the table are defined as follows:
 
 You can also access the detection result programmatically via our [public API](/api/resources/radar/subresources/bgp/subresources/hijacks/subresources/events/methods/list/) ([CC BY-NC 4.0](https://creativecommons.org/licenses/by-nc/4.0/) license).
 
+## BGP real-time routes
+
+Cloudflare Radar's prefix routing page displays real-time BGP routes as a [Sankey diagram][sankey]. This visualization is built using MRT data from [RouteViews][route-views] and [RIPE RIS][ripe-ris], combined with real-time streams from RouteViews' Kafka instance and [RIS Live][ris-live].
+
+By default, the route visualization shows paths from the originating AS to [Tier-1 networks][tier-1], omitting the segments from Tier-1 networks to BGP route collectors for clarity. Users can choose to see the complete paths using the "Show full paths" toggle.
+
+Above the visualization, a table details the prefix origin, including the originating AS, its visibility percentage across route collectors, and [RPKI][rpki] validation status (`valid`, `invalid`, `unknown`).
+
+Hovering over a link in the diagram reveals a tooltip with the connected ASNs, the observing BGP route collectors (from [RIPE RIS][ris-collectors] and [RouteViews][route-views-collectors]), and the last update timestamp.
+
+[route-views]: https://www.routeviews.org/routeviews/
+[route-views-collectors]: https://www.routeviews.org/routeviews/collectors/
+[ripe-ris]: https://www.ripe.net/analyse/internet-measurements/routing-information-service-ris/
+[ris-live]: https://ris-live.ripe.net/
+[ris-collectors]: https://ris.ripe.net/docs/route-collectors/
+[sankey]: https://en.wikipedia.org/wiki/Sankey_diagram
+[rpki]: https://blog.cloudflare.com/rpki-details/
+[tier-1]: https://en.wikipedia.org/wiki/Tier_1_network
+
 ## Certificates
 
 Encryption is a critical part of a safe Internet. SSL/TLS is the standard security technology for establishing an encrypted link between a client and a server.