Short answers, pulled from the story.
Glorantha was created by Greg Stafford, who first began developing it in 1966 while studying at Beloit College. He conceived it as a vehicle for deepening his own understanding of mythology by constructing a mythology from scratch.
The first game set in Glorantha was the board wargame White Bear and Red Moon, published by Chaosium in 1975. Notably, the game did not use the name Glorantha; the name appeared in print for the first time in 1978, in issue four of the newsletter Wyrm's Footnotes.
Magic in Glorantha operates at every level of existence, from everyday prayers and charms up to the forces that created and maintain the world. Competing magical outlooks, including theism, shamanism, and mysticism, each offer distinct explanations of reality, and none is treated as objectively correct.
Gloranthan elves, called Aldryami, are plant people who are physically plant-like and hostile to humans, in sharp contrast to the wise, noble elves of Tolkien. Gloranthan dwarves, called Mostali, are literally made of stone and exist as expressions of rigid laws of creation, rather than the gruff craftsmen of Tolkien's tradition.
A third edition of RuneQuest was published with Avalon Hill in 1984, but it defaulted to a 'Dark Ages of fantasy Europe' setting rather than Glorantha. The relationship between Chaosium and Avalon Hill broke down entirely in 1995, and Avalon Hill's subsequent RuneQuest project, RuneQuest: Slayers, was canceled just before printing in 1998.
King of Dragon Pass is a video game released by A Sharp in 1999, set in Glorantha's Dragon Pass region. Players take the role of an Orlanthi hero seeking to unite the clans and tribes of Dragon Pass into a single kingdom, and the game was noted for its depth of coverage of the setting and its portrayal of Stafford's ideas about the heroquest.