This means whether or not the flight path that you are following may intersect the other airplane’s path.
For example, when you scan for traffic (look for other airplanes while you are flying), you must include looking up and down in all quadrants that you can see.  The pilot becomes adept at determining whether or not another aircraft is “a factor.” This means whether or not the flight path that you are following may intersect the other airplane’s path.  If so, heading in a different direction or climbing or descending would be a good thing to do to avoid meeting the other craft.