Joel started 5 miles west of home, and ended 5 miles east of home. how far did he travel?

His displacement ... the distance between his start point and
his end point ... was 10 miles.  But we don't know what route
he followed on the way, so we don't know how much distance
he actually walked or drove.  It couldn't be less than 10 miles,
but it could be any distance more than 10 miles.