Part of taking great photos is "capturing the moment", and "being in the right place at the right time" However when you see that
"One" fantastic photo, you'll soon realise that the photographer may have taken HUNDREDS of the same scene, but "that one" captured the moment.
Also then when you have "that one" a lot of other things like cropping the photo, colour balancing and a bit of photoshop trickery may have been done to make it that extra bit special.
here's an example.
original
and
tweaked
one is an "Ok" photo, however the second has much more impact.
a bit of cropping, adjusting the colour saturation, brightness / contrast and blurring out the background to draw your eye
to the action.
All of this goes into making an average photo better.