The mission to kill Osama bin Laden was carried out by a highly trained, highly secretive group of Navy SEALs working with the CIA. The SEALs group is known as Team Six. Officially, Team Six doesn't exist. Unofficially, they're "the best of the best." Here, a brief guide:

What makes Navy SEALs so special?
The Navy SEALs (which stands for Sea, Air, and Land) have their "origins in World War II when the United States realized that to invade Japan, it needed savvy, quick-thinking fighters who could perform reconnaissance at sea," says Ashley Fantz at CNN. The SEALs eventually "became known as jack-of-all-trade soldiers" with immense physical strength and "tactical expertise." To become SEALs, candidates train 18 to 24 months, including a grueling "Hell Week" during which they are "constantly cold, hungry, sleep deprived, and wet." The dropout rate for SEAL training is about 90 percent. There were 2,500 active-duty SEALs as of 2009.

And what is Team Six?
It's the unofficial name for a group of elite SEAL "badasses," says Robert W. Johnson at Business Insider. Its members all "exist outside military protocol, engage in operations that are at the highest level of classification, and often outside the boundaries of international law." Team Six is part of the Naval Special Warfare Development Group, or DEVGRU, based in Dam Neck, Va. "SEAL Team Six actually works so often with the intelligence agency that it's sometimes called the CIA's Praetorian Guard," says Kimberly Dozier of the Associated Press.

How did Team Six get started?
The group has its origins in the wake of the failed 1980 attempt to rescue American hostages held in Iran, and was codenamed Team Six to confuse Soviet intelligence about how many SEAL teams really existed. (There were only two others.) Members of Team Six are recruited from other SEAL units. "Getting on a special team means you've established yourself as a mature and steady operator with a real world track record of high-stakes, sensitive missions," says one former SEAL, as quoted by CNN. Even so, the training for Team Six is so intense that the attrition rate is reportedly nearly 50 percent.

How many SEALs were on the mission to get bin Laden?
Reports vary, but there were apparently a few dozen.

Were they excited about the mission?
Yes. "The word is that when they heard that bin Laden was their target, there was a huge cheer that went up," says Eric Greitens, a former SEAL and author of The Heart and the Fist, as quoted by MSNBC.

Will the SEALs who killed bin Laden ever come forward?
That seems highly unlikely — publicity is not the SEALs' style. In fact, they call themselves "the quiet professionals." "There is no room for braggarts in the SEALs," says Chris Heben, a former SEAL, as quoted by CNN. "Talking hurts missions and gets people killed."

Sources: ABC News, Associated Press, Business Insider, CNN, National Journal, MSNBC