Suppose you need to calculate the distance between two points, each of the points has three coordinates. Say, A(x1,y1,z1) and B(x2,y2,z2). There's the following formula: AB=sqrt((x2-x1)^2+(y2-y1)^2+(z2-z1)^2). That's how to calculate distance in three-dimensioned space (i.e. having three coordinates for each point).