Short answers, pulled from the story.
RuneQuest was designed by Steve Perrin, Ray Turney, Steve Henderson, and Warren James, and first published in 1978 by The Chaosium. It is set in Greg Stafford's world of Glorantha, which Stafford originally created for the 1975 board game White Bear and Red Moon.
RuneQuest is built around percentile dice, meaning players roll a hundred-sided die against a target number equal to their skill percentage. Success and failure are further subdivided into critical success, special success, success, failure, and fumble, each calculated as a fraction of the target number.
Unlike Dungeons and Dragons, RuneQuest does not use character levels or class-based advancement; characters improve individual skills directly through play. Combat tracks hit locations on the body rather than abstract hit points, and all adventurers have access to magic regardless of class.
Glorantha is the default setting for RuneQuest, created by Greg Stafford. The Dragon Pass region is the core play area, comprising five homelands including Sartar, Prax, Old Tarsh, Lunar Tarsh, and the Grazelands. Religion is organized through cults with three tiers of membership, and the basic rules describe twenty-one such cults.
Basic Role-Playing, or BRP, is a simplified and generic version of the RuneQuest system, published by Chaosium in 1980 and edited by Greg Stafford and Lynn Willis. It served as the engine for many Chaosium games, including Call of Cthulhu (1981), Stormbringer (1981), Pendragon (1985), and Nephilim (1992).
Chaosium licensed RuneQuest to Avalon Hill in 1984, which published a third edition set in the Dark Ages of fantasy Europe rather than Glorantha. The edition was poorly received and did not meet sales expectations. After Hasbro acquired Avalon Hill in 1998, the RuneQuest trademark eventually returned to Chaosium-aligned ownership, and a new edition, RuneQuest: Roleplaying in Glorantha, was released in 2018.