What was discovered? 

The amazing goal by Roberto Carlos for Brazil against France in 1997 was scored from a free kick 115 feet (35 metres) away from the goal!

The spin on the ball as it passed through the air allowed it to follow a curve as it approached the goal.  Air resistance due to atmospheric molecules helped to slow down the ball, but many people thought that the final twist of the ball into the goal must have been caused by a gust of wind. 

Not so, according to experiments which showed that the slowing effect of air molecules allowed the spin of the ball to have a much greater effect on the curved path into the back of the net...

The amazing goal was due to the skill of the player, and not some random gush of wind! 

Watch the amazing goal here!

How?

Of course it was not possible to have Roberto Carlos repeat his amazing feat many more times, so the next best thing was to set up a model:

A sling shot was used to hurl tiny plastic ball through water and the velocity and spin of the ball was recorded along with the path it followed (the trajectory)

See more in this BBC article with videos including comments by Dr. Andy Harland

Why is it important?

Ha!  Any football fan will agree that the skill of a player in such a moment is breathtaking, so to have the event confirmed by science should warm the hearts of millions... and enlighten us to the trajectory  of spinning objects too!