in introduction to 3 dimensional geometry, Section Formula, whats the difference between dividing the line segment internally and dividing the line segment externally ?

let $P(x_1,y_1,z_1) and Q(x_2,y_2,z_2)$ be two points in the space and let R be a point on the line segment joining P and Q such that it divides the join of PQ internally in the ratio m : n. then
the coordinates of R are : $(\frac{m{x}_2+n{x}_1}{m+n},\frac{m{y}_2+n{y}_1}{m+n},\frac{m{z}_2+n{z}_1}{m+n})$

if $P(x_1,y_1,z_1) and Q(x_2,y_2,z_2)$ be two points , and let R be a point on PQ produced dividing it externally in the ratio m : n.
then the coordinates of R are $(\frac{m{x}_2-n{x}_1}{m-n},\frac{m{y}_2-n{y}_1}{m-n},\frac{m{z}_2-n{z}_1}{m-n})$

hope this helps you.