The Ferengi hold the title of Star Trek's only culture based entirely on commerce. They can be visibly identified by their bulbous heads, sharp teeth, and oversized ears, and otherwise identified by their tightly-closed wallets and ethically dubious but always lucrative business contracts.
According to the DS9 episode “Little Green Men,” Ferengi history began over 10,000 years ago. Their history is reportedly clear of human characteristics like genocide and slavery, although it's questionable that a profit-based society could have developed without attempting the latter (note: DS9 “Family Business” makes mention of indentured servitude as a punishment for the most severe of crimes). The Ferengi greatly expanded their potential consumer base by purchasing warp technology, and their primary main mode of interstellar transportation is the D'kora-class starship, which is slightly crescent-shaped with a long frontal protrusion. After leaving their homeworld of Ferenginar, the Ferengi opted not to limit their market by aligning with any of the major interstellar organizations. Instead, they renamed their present government the Ferengi Alliance (under the control of the Grand Nagus), and they continued the profit-based culture they'd been developing for 100 centuries. Their culture is based upon the Laws of Acquisition.
The isolationist practices of the Ferengi have opened as many doors as they've metaphorically closed: occasionally, a Ferengi representative will accompany the diplomat of another planet or organization in the hopes that crossing trade barriers will ultimately lead to better relations. This puts the Ferengi in a position to profit from the intergalactic tension, and if there's one thing a Ferengi loves, it's profit.
On Ferenginar, worldly wealth crosses over the great divide. The Ferengi have developed a commerce-based religion that promises reincarnation to those who have been successful before their death by allowing the deceased to bid on his next life using the money he accumulated in his last. This implies a karmic cycle that's difficult to break out of.
One of the many questionable policies of the Ferengi Alliance is their insistence that all Ferengi women remain unclothed and homebound. Recently, this policy has been relaxed, but the tension is far from resolved. It is implied that the rights of women will improve with Nog as the new Grand Nagus.
Another noder described the etymology of the word “Ferengi,” but it's worth noting that the source words still receive a great deal of usage in Southeast Asian countries like Thailand and Malaysia.