A dilation is simply a change of size. The preimage (original figure) and the image are similar (meaning also that all corresponding angles are congruent), so the dimensions remain proportional but not equal unless the scale factor is one, sides remain parallel, orientations remain the same. Unless a side passes through the centre of dilation, sides and their images are not collinear.
Finally, if we define betweenness of a point Q collinear with points P and R such that Q is between P & R, then betweenness is also preserved because line segments are mapped into line segments.
