To make an eagle, which simply means shooting two strokes under par on a hole, you need a combination of luck and skill. It's a difficult feat. Even for professionals, eagles don't occur that often. But with enough luck and enough practice, it is possible.
Definition of an Eagle
If you holed your ball in three shots on a par-5, that's considered an eagle.
Another eagle would be if you holed your ball in two shots on a par-4. A hole-in-one on a par-3 is also considered an eagle, but is almost always referred to as a hole-in-one.
Why is it Called an Eagle?
H.B. Martin's book, "Fifty Years of American Golf," provided an account of a foursome match at the Atlantic City, New Jersey, Country Club. After a well-played hole, one of the players said, "That was a bird of a shot." The term "eagle" originated from the term "birdie," which from then on meant shooting one stroke below par on a hole. An "eagle" was then recognized as shooting one better than a birdie.
Eagle on a Par-5
Eagles are most commonly made on par-5s.
The traditional eagle on a par-5 starts with a long drive and a second shot that carries the ball to the green. You have to make the putt on the third shot. You can also chip in or hole the ball from the fairway on your third shot to make an eagle.
Eagle on Shorter Holes
It's possible to get eagles on par-4s and par-3s, but it's far less likely.
On par-4s, you'll need to hole your second shot, which is usually not close to the green.
It's uncommon for golfers to hit the ball onto the green on their tee shot, though it can be accomplished on a short par-4. For an eagle on a par-3, the formula is simple: shoot a hole-in-one.
Double Eagle
A double eagle, also referred to as an albatross, is when you shoot three shots below par on one hole. The score is uncommon. To accomplish it, you'll need a hole-in-one on a par-4 or hole your second shot on a par-5.