Similar polygons have the same shape, but not necessarily the same size.  One figure is a dilation of the other.  If the scale is larger than 1, the second figure is an enlargement. If the scale is between 0 and 1 then the dilation shrinks the original figure.  If the scale equals 1, then the figures are congruent.

http://www.mathopenref.com/similarpolygons.html

 

 http://www.mathopenref.com/similartriangles.html

 

http://www.mathopenref.com/similartrianglesparts.html

 




http://www.virtualnerd.com/algebra-1/linear-equations-solve/ratios-proportions/similar-figures-indirect-measurement/indirect-measurement-example

http://www.virtualnerd.com/geometry/similarity/parallel-lines-proportional-parts/practice-triangle-proportionality-theorem