Thrall, (commonly misspelled) is the current Warchief of the Horde. He can be found primarily in Orgrimar's valley of wisdom. He was a prisoner of the internment camps of Lordaeron as a baby. A human child of a servant in the camp named Taretha Foxton was the first person to realize he was a baby. After this discovery he was nursed by Tarethas mother and was considered as Blackmoores' "pet orc". He led the orcs escape from the internment camps and across the ocean to the current day Durotar. His first friendship with a human so long ago is part of the reason he would accept peace for both Horde and Alliance.
Now Thrall is no longer part of the Horde, technically. He has given the mantle of Warchief to Garrosh Hellscream, son of the hero Grom Hellscream. He did this so he could devote his time to helping the Earthen Ring fight against Deathwing the Destroyer. He can be found at the Maelstrom, trying to repair the damage, but also in various other zones for the elemental bonds quest chain. He has long had a fan fiction relationship with Jaina Proudmoore, but developers gave him a random orc woman named Drakka.