Earth

Earth was a world on an alternate Material Plane.

Geography
This planet was comparable in size to Abeir-Toril,  making its equatorial circumference about. The cloud cover of this planet resembled that over Radole. One of the major landmasses of it was known as Eurasia.

Toril was slightly larger than this planet, but it had less mass so the difference in gravity was negligible.

Fauna
One source falsely claimed that foxes were never native to Toril, and were actually brought from France by an adventurous halfling trader named Altho Minstrelwish around 12 DR. However, it was explicitly known that foxes existed on Toril far before the 1st century DR, even in the times of ancient Netheril.

Much like on Toril, there were a variety of animals on this planet that people harvested ivory from. This included the tusks of boars, elephants, narwhals, walruses. As well as the teeth of hippopotami and cachalots.

There were some breeds of dog on this world that were unique to it and difficult or impossible to find on others like Toril, such as Boston Terriers and Irish Setters.

Gateways
Elminster Aumar claimed that there existed hidden portals not only between Earth and Toril, but to the planets of Krynn and Oerth.

People
A number of human peoples of Faerûn originally came from another world, which is widely believed to have been Earth. To replenish their population after a devastating plague, the mages of the Imaskar Empire in Faerûn opened two great gates to this other world, and kidnapped numerous humans to serve as their slaves. Those of Mulhorand hailed from a desert land given life by the seasonal flooding of a great river and those of Unther from another land. After transporting them back to Abeir-Toril, the Imaskari closed the gates forever. Intermarrying both with each other and the Imaskari, they became the Mulan. With them, they brought their own societies, mature culture, and later, the gods of the Mulhorandi and Untheric pantheons.

Later came a people from two lands: a collection of city-states known for their daring philosophies and a land of empire and glory; they had similar pantheons of gods. These were followed by folk from a rugged land with a culture tied to nature, the sea, and the warrior history of its dozen-king greater god. These brought their own societies and faiths, and settled around the time of the rise of Netheril.

In the Year of the Prince, 1357 DR, an inhabitant of Earth called Ed of the Greenwood assembled various journals, maps, and other works from Elminster Aumar into the first publication of the Forgotten Realms campaign setting.

In the Year of Shadows, 1358 DR, Amelior Amanitas agreed to a request by Elminster, due to him generously sheltering Amelior after some incident in Volkumburgh, to provide author Jennell Jaquays the wealth of information he had regarding the the North and its history. This culminated in the sourcebook The Savage Frontier.

In a note to one of Ed of the Greenwood's fellow authors, Elminster described the building style of merfolk as being comparable to that aforementioned collection of city states, due to their emphasis on columns and carved works.

Laeral Silverhand also regularly traveled to Earth to visit Steven E. Schend and spoke to him of Waterdeep, even if she did tend to interrupt his writing. He compiled the lore into articles for Dragon magazine.

Deities
A number of gods of Egyptian pantheon and the Babylonian and Sumerian pantheons of Earth traveled to Toril and formed the Mulhorandi and Untheric pantheons, respectively. The Greek pantheon was largely unknown in the Realms, with some exceptions. For instance, Poseidon had a small following on Toril and Hephaestus had a book written about him, though he was considered an obscure deity.

A number of deities within the Realms originated from the Celtic pantheon and Finnish pantheon. Many of the deities within the Lords of Creation, the major pantheon worshipped in the Kuong Kingdom, hailed from the Vedic pantheon, such as Garuda and Yama.

A number of animal spirits, foremost among them Eagle and Raven, were worshiped both by the green elves of Toril and the American Indian peoples of Earth.

Gemstones
Much like the Realms, on this planet people cut gems found in massive form down into gemstones if they were of high value. These gems included agate, beryl, chalcedony, grossular, idocrase, jade, jasper, rhodonite, rock crystal, rose quartz, serpentine, tiger eye agate, and tourmaline. If not of high value gems were typically weaker and they would be sold by weight for carving application. These gems included amber, jet, malachite, moonstone, obsidian, opal, and turqoise.

Others gemstone shared by Toril and Earth included bluestone, which was sometimes known on that planet as "ditroite", and serpentine stone, which was usually known on this planet as "verde antique."

Besides using them for adornment, the people of this world had gemstones serve as representations of their deities or guardian spirits, for healing, for divination, repositories of spells, or protective charms against magic and evil creatures. Some of their legends spoke of gems forming from tears, growing on trees, being excreted by horses, or being spat out by a deity or hero.

Notable Locations
The Pecos River was a river on Earth. St. Sollars the Twice-Martyred described the demon lord Orcus, Prince of the Undead, as "the meanest dude this side o' the Pecos".

The wizard Elminster's favorite place to relax and find rest off Toril was found in Yellowstone National Park on Earth. He kept a magic portal there from his hideout within the planet Coliar, specifically to the Earth year 1894 AD. It was also here that he purchased German beer to sell to his friend Gamalon Idogyr.

Trivia
Alaska was used as a cheat code in the game Blood & Magic, which when used would summon a gnome unit.