Line passing through the point A(a1,b1,c1) parallel to the vector V1(p1,q1,r1)
Line passing through the point B(a2,b2,c2) parallel to the vector V2(p2,q2,r2)
where a12 = (a1 - a2), b12 = (b1 - b2) and c12 = (c1 - c2).
The distance between two straight lines on a plan is the minimum distance between any two points lying on the lines.
The distance between two parallel lines is the perpendicular distance from any point on one line to the other line.
The distance between two intersecting lines is eventually comes to zero and
The distance between two skew lines is equal to the length of the perpendicular between the lines.