Gielinor (sometimes confusingly referred to as "RuneScape" by characters in-universe) is either the world or the actual "mainland" continent RuneScape takes place on. It's never really clear, but seeing as
how the game has multiple continents now, Gielinor refers to the mainland upon which most of any given campaign will take place. The continent was named by Guthix apparently. I guess thats who you blame for the "religion" anagram thing.
The mainland of Gielinor is made up of several kingdoms; Misthalin is the oldest, Asgarnia is the richest, and
Kandarin is the strangest. These three kingdoms are sometimes called "the Sisters" in common
parlance due to their historical, economic, and cultural connections with eachother.
Misthalin is the oldest continually inhabited region of Gielinor, with the most ancient city of Saranthium being founded at the start of the First Age. Today,
Misthalin is known for being Gielinor's breadbasket; cool and wet in climate, the incredibly fertile soil is nourished by the region's many rivers, especially the River Lum, whose origin comes all the way from the frigid
mountains of Troll Country far on the northern end of Gielinor.
Misthalin may not be particularly wealthy compared to the other Sister Kingdoms, but its food and beer are legendary, and some of Gielinor's finest craftsmen come from
the many small, self-sufficient duchies and hamlets throughout the kingdom. Varrock is considered the economic heart of the entire world and is Misthalin's ancient capital, uniquely prosperous and extremely
developed, with a royal family who are notorious patrons of the arts and the church; Varrock is a hub of radical new ideas and of culture, and is the enviable jewel of eastern Gielinor.
Asgarnia is the youngest of the Sisters, permanently settled at some time in the mid Third Age. She's also the wealthiest, with a uniquely central location
within Gielinor, making her particularly attractive as a location for trade and commerce. Helpfully, Asgarnia is thoroughly safe and heavily patrolled by the kingdom's colossal army
(It's said one could walk the length of the kingdom with a gold plate on their head without fear of being robbed). Queen Vallance III rules from the pristine white fortress city of Falador, headquarters of
the elite Armasyne Order; better known as the White Knights, Gielinor's most prestigious and feared royal guard.
The Southern Sea on the southern coast
makes Asgarnia extremely wealthy in sea-bound trade, and makes it Gielinor's most significant naval power. In the far-off Tropic of Marimbo, there is a colony called Queensport on the
Isle of Hounds established by Queen Vallance II, though recently the crown has lost control of this harbor, now ruled by a significant pirate lord. Asgarnia imports most of its food from Misthalin, and
in exchange, Asgarnia bears the responsibility of being permanently paranoid about invasion from trolls in the north to piracy from the south, as well as potential danger from east and west. Falador is
rather famous for its paranoia about losing all that it has built to war, though that's perhaps understandable when one has to patrol a massive border on every side.
Kandarin has a reputation for being not quite like the other two sisters east of White Wolf Mountain; magic is used very often and the cultures and political
divisions are often hard for people not from Kandarin to ever fully understand. It's the most diverse kingdom, home to humans, dwarves, gnomes, elves, goblins, and giants. Things are often not quite right,
though you don't know much about Kandarin at present. To the far western edge of the kingdom lie the ruins of Thammaron, the ancient capital of the Great King Zamorak (incidentally, Kandarin is the only
place where worship of Zamorak is relatively common).
To the south of Kandarin are the Feldip Hills, a region of dense jungle and volcanic activity home to Gielinor's giant and ogre population. One might call it "Giant Country",
except that giants do not seem to understand the idea of a kingdom; this is where they roam, so it remains technically just a part of Kandarin. Travel west from Ardougne, and one finds Hazelholm, a
colossal hedge labyrinth housing the royal city of the gnomes within its walls. Unofficially, the entire western half of Kandarin is more or less mostly full of gnome settlements and is basically its own
gnomish kingdom, but gnomes seem more content to play and be silly than worry about state-building.
The Fremennik Provinces are an ungovernable ethnographic region on the northern coast of Kandarin and hugging the thin snowy coast of Troll Country, swallowing the
entire Lunar Sea in its territory. The Fremennik are fair haired, blue-eyed, sea-bound raiders and settlers who are known for their love of fighting, hatred of magic, and slow adoption of the worship of
the gods. Oral histories of the Fremennik are plentiful, but very few have committed to writing anything about their culture down, especially not people from outside the Fremennik Provinces. What is known
is that they either are a clan of humans who migrated north, possibly to escape some conflict around the Second Age, or they could have migrated from somewhere beyond the northern seas and settled the islands
off Gielinor's coast before slowly moving to the mainland.
The Fremennik Provinces are called such because there is no one unified "Fremennik" kingdom. Vicious, bitter, bloodline-based skirmishing and factionalism has wracked the Fremennik since the time of the
Runic Crusades in the Second Age, where clans and tribes of Fremennik embarked on a crusade to the south to the current regions of Asgarnia and Misthalin to slay wizards and stop the creation of runestones, as
commanded by Fremennik high chieftain Freydir the Unwise (a term of flattery in Fremennik culture). Fremennik aversion to the use of magic may have its roots in trauma and legend of its effects on the army of
Thammaron, which some ethnographic scholars from Royal Academy of Avarrocka interpret to mean that the Fremennik may have in fact originated as ancient peoples of the Zamorakian Empire who migrated north
in the early First Age to escape the God Wars. This is highly disputed as no archaeological evidence supports this claim, and humans that historically inhabited the regions of the Zamorakian Empire the
Fremennik could have come from were not
extremely blonde and pale.
The largest and most powerful of the clans formed into the settlement of "Rellekka", a city which appears to be full of grim, towering giants who don't understand magic let alone much else beyond fighting.
However, Rellekka is the most "progressive" of the Fremennik clans, as they mostly tolerate the use of magic, and efforts to open the first Church of Saradomin in the Fremennik Provinces have been progressing
smoothly. In the mountains to the north east lie the far more conservative Fremennik, attempting to distance themselves as much as possible from the lax morals of the Rellekka clan. Paradoxically, it seems that
the worship of Guthix in some of these remote communities has been ongoing for a long time, despite their utter hatred of magic.
Morytania is a land ruled by vampyres, albeit quarantined inside their prison-kingdom by the blessed
River Salve. In the Fourth Age, Misthalin was nearly destroyed by an invasion of vampyres, but were fended off after a century-long occupation by Drezel, a legendary paladin of Saradomin. The blessing
on the River Salve was his doing.
Forinthry is a cursed wasteland that was once home to an immense empire in the Third Age. More generally known as "the wild north" or "the wilderness".
Troll Country is a series
of polar mountain ranges where Gielinor's Troll population resides. Trolls eat humans and choose to live by themselves in caves, so the Northern Wastes region has been more or less given to them. Some
dwarven settlements exist here, most notably Keldagrim at the base of Trollheim, though you enter through the Fremennik Provinces, so it doesn't really count.
Finally, at the farthest, most remote edge of Gielinor is the rugged Arandar Pass, sheltering the kingdom of Tirannwn in its benevolent shadow. Elves live there.
Humans that visit rarely come back, let alone even find their way in. Tirannwn is the most mysterious and secluded part of Gielinor, which may be by design. Elves
do not frequently leave.