Bag Vendors (sometimes called Bag Merchant) are NPC vendors that sell bags ranging in size typically from 6 to 12 slots.
Bags that can't be purchased from vendors are typically crafted, if not quest rewards.
Thrall led the orcs to the continent of Kalimdor, where they founded a new homeland, naming it Durotar after Thrall's murdered father. Rising above their past bloodshed and demonic curse, the orcs built a society based on survival and prosperity rather than conquest.
Named after the former Warchief, Orgrim Doomhammer, Orgrimmar was constructed in a short amount of time, with the aid of goblins, tauren, trolls, and Rexxar.
Today, Orgrimmar lies at the base of a mountain between Durotar and Azshara. Times have changed though, since Garrosh's reign as Warchief--he has alienated several races due to his aggressive and insecure nature. Post-Cataclysm Orgrimmar has also been expanded and reinforced with many protected metal spikes.