What it means is that we are a tiny speck of dust floating on a tiny rock in space and an object that has come from a distance that is so far away numbers wouldn't do it justice has just flew by earth closer than the distance between the earth and sun (1 AU). Some quick facts (from wikipedia), 100 years ago it was 561 AU away (Neptune is ~30 AU), its max speed was 196,000mph and when discovered it was going 'only' 100,000mph. Space/Astronomy is a beautiful thing when it comes to relative perspective to us humans.