From what I’ve seen it is basically a managed and updated feed of indexers that it keeps synced with you *arr apps. The *arr apps are the ones that do the searching based on whatever indexers they have imported from prowlarr. They use different criteria like media quality or profiles I think is what they are called.

Searching prowlarr itself would simply provide you with all results from the different indexers, you can filter results/queries if based on different things/tags but I tend to not use it directly myself.

I’ve found *arr wiki to be really useful when learning how to set things up correctly.

Prowlarr is an indexer manager/proxy built on the popular arr .net/reactjs base stack to integrate with your various PVR apps. Prowlarr supports management of both Torrent Trackers and Usenet Indexers. It integrates seamlessly with LazyLibrarian, Lidarr, Mylar3, Radarr, Readarr, and Sonarr offering complete management of your indexers with no per app Indexer setup required (we do it all).

I’ve had Sonarr & Radarr working for years now with Sabnzbd (+provider & indexer) & Qbittorrent… but hadn’t ever bothered to look up things like Readarr / LazyLibrarian, Mylar3 and Lidarr.

I’ve learned about a lot more possible things to do from your simple question post, thanks!