Distance between 3D points

Distance between 3D points equals the square root of sum of sqares of diferences between similar coordinates:

distance = sqrt( (x2-x1)*(x2-x1) + (y2-y1)*(y2-y1) + (z2-z1)*(z2-z1) )

where x2 = x of point2; x1 = x of point 1.