Debrid help

Currently have Stremio + Torrentio up and running. Good internet speed but it's currently unwatchable with all the buffering. I have been using OnStream as it's a great APK with little to no buffering time but recently they've included a small amount of adverts. Don't have much of an understanding of debrid etc. Could someone please give me an ELI5 (or give me a link with a good description) as to:

Is debrid required to reduce buffering times How to install debrid Is debrid free