double eagle, that's correct for the USA but here in the UK 3 under is classed as an Albatross
Scoring terms summarised
+1 = Bogey (then this goes up - ie. double bogey, triple bogey etc etc)
+/-0 = Par
-1 = Birdie
-2 = Eagle
-3 = Albatross (Double Eagle)
-4 = Condor
-5 = Ostrich (almost impossible as this would require a hole-in-one on a par 6 which on their own are very rare)
5 under par
In golf a birdie is one under par on a given hole. So a 2 on a par 3, 3 on a par 4 and 4 on a par 5.
The highest par in golf is 5. A seven is a double bogey on a par 5 and a triple bogey on a par four and a quadruple bogey on a par 3.
A double eagle on a par 5, a hole in one on a par 4, and a lie on a par 3.
It means that you got 3 under par on a hole So got a 2 on a par 5 or a 1 on a par 4.
4 under par is known as a "Condor".
A birdie is a hole played one stroke under par.
To get under par.
Yes.
Every hole has a par rating - usually 3, 4 or 5. One under means one less than this. So on a par 4 hole a score of 3 is one under par. This is called a birdie.
Golf This is a Bristish term in golf for completing a hole three shots under par. Otherwise known as a 'double eagle'. e.g. Getting the ball in the hole in the hole in 2 shots on a par 5 hole. Acheiving this is VERY rare. 'Par' is the number of shots you would be expected to have to take to complete a hole in a game of golf.
Depending on the golf course, the set par can be anything, but it is very common for the par to be 3 and 4