Coil is a web monetization effort where you subscribe for $5 a month and get access to various exclusive content things on participating websites. I think of it like Brave meets Patreon.
Firefox Reality is “mixed reality” (AR/VR) games and experiences from around the web.
The news here is that Mozilla is adopting Coil to experiment with monetization on Firefox Reality. Coil is for-profit, which adds a wrinkle to things. It uses Interledger to move money, which means creators can work in whichever currency they like. Lots of details and explanations in the linked post from Mozilla’s blog.