The concept of right of way is one that applies to foil and sabre. Wikipedia actually has a decent definition for this concept: Priority or “right of way” is the method used in foil and sabre fencing to determine which fencer receives the point if both fencers land a valid hit at the same time (if both fencers land a valid hit at the same time in épée fencing, they both receive a point). Generally, priority is determined by first considering which fencer attacked first. In order to initiate an attack a fencer must threaten the target area of their opponent with the point of the foil while their arm is extending. When performing a compound attack the fencer must not withdraw the arm by bending the elbow.
Below is a video of a demonstration done by Tim Morehouse and his cohorts at a recent Fencing Masters event in New York. It gives a good introduction into what right of way looks like when watching a bout. Understanding right of way will help you to understand how you can score points in a bout.