One under par for a hole is one shot less than par, say you make a 3 on a par 4, this is a birdie. One under for a round is where you had a round which was one shot less than par, say you shot 71 on a par 72.
For holes played, or for that round, or for the tournament, the player has taken one less shot to play those holes than par.
A par is a certain ammount of strokes you hit the ball with in Golf. If you hit under the ammount of par it is reffered to as an under par. Which is different depending on the difficulty.
The Philadelphia Eagles. In Golf, an Eagle is 2 strokes under par.
Eagle
A score for one hole that is one under par is an, "Eagle".
An Eagle in golf is lower than a birdie. A birdie is 1 stoke below par on the hole and an Eagle is 2 strokes below par For example, on a par four, an eagle is two strokes on a par three, an eagle is not used. it is just referred to as a hole in one!
"Bird" was a slang term for 'good' in the 19th century and so a great shot on the golf course became known as a 'bird', which then turned into 'birdie'. It was used for any under-par score at first. Then, 'eagle' was added to maintain the avian theme and it differentiated a shot of two under par, from the 'birdie', which was one under par. An extremely rare three under par shot is now called an 'albatross' (aka 'double eagle').
Each hole at golf has a standard number of strokes (number of times the ball is hit) to get it in the hole. This number is called Par, taken from the par value of stock. For example, if the standard number of strokes for a hole is four, it is called a Par four hole. If a player gets the ball in the hole in one less than (one under) Par, it is called a Birdie. Legend has it that a famous player's ball hit a bird in mid-air and he then completed the hole in one stroke under and the term Birdie was born. Making the hole in two strokes under Par is a larger bird so it's called an Eagle. Three strokes under Par an Albatross, because an Albatross is such a rare bird. If you take one more stroke than Par it's call a Bogey, after the Bogey Man. Two strokes over is a Double-Bogey. Three is a Triple-Bogey.
An eagle is two strokes under par, a birdie is one stroke under. An eagle is a better score.
Albatross.
The guideline is how many strokes you are under par. So on a par 4, which is under 2 strokes, - 2, its called an Eagle. Holing it out in 1 on a par 4, - 3 strokes is an Albatross.
Eagle.
The term "eagle" means scoring two under par (−2). Eagles usually occur when golfers hit the ball far enough to reach the green with fewer strokes than expected. This most commonly happens on par fives, though it occasionally occurs on short par-fours. A hole in one on a par-three hole also results in an eagle. The name is simply analogous to a birdie (see above); the name "eagle" was used as a larger bird representing a better score.
Par is the regulation score for a hole in golf. A player would find the green in regulation, and have two putts, well that is the idea.