Abeir-Toril ("cradle of life"), or Toril as it's better known, is the planet of the Forgotten Realms campaign setting. Toril is approximately the size of Earth, and has one moon, Selûne. The star around which Toril orbits doesn't appear to have a particular name (other than "Sun").
Toril has numerous continents. For some reason, they're ordered almost like Earth continents, but are shaped quite differently. Foremost, there's Faerûn, a subcontinent of the largest continent on the planet, set in its western corner, roughly (if this were Earth) on the place of Europe. (Faerûn is the place described in the Forgotten Realms Campaign Setting book.) The same continent also has the large area of Kara-Tur in east and Zakhara to south. Across the ocean is Maztica. Faerûnians don't often get to other places, even when the rumored riches there are interesting indeed, because of the hostility of the inhabitants, well guarded borders, and the many dangers of the travel.
The planet also has a lot of lands with no name or description. The obvious reason is that the DMs are free to make whatever they want on these areas, and Wizards of the Coast is not going to put things there.
Ed Greenwood created Faerûn, but the name Toril was invented by Jeff Grubb (originally name for his own campaign). Apparently, the full name "Abeir-Toril" was added because they wanted the first entry in the alphabetical index to say something about the world.
Anonymous. "Interview of Jeff Grubb". Dragonlance Nexus, 29/4/2001. Online. <URL:http://www.dl3e.com/inn/companionsdisplay.asp?id=11253>. Accessed 2003-01-12.
Ed Greenwood, Skip Williams, Sean K. Reynolds and Rob Heinsoo. Forgotten Realms Campaign Setting, 6/2001. Wizards of the Coast, Third edition, 6/2001. ISBN 0-7869-1836-5.
Jeff Grubb. "The Origin of the Name 'Toril'". Yet Another Forgotten Realms Page, 12/5/2001. Online. <URL:http://www.geocities.com/TimesSquare/Castle/2566/jg-toril.htm>. Accessed 2003-01-12.