If two figures are congruent, they are similar; but not vice-versa.
In the first graph (top left), notice that all the corresponding sides of both figures have the same length; therefore, they are congruent.
Graph 1 (top left) consists of a pair of congruent figures; therefore, they are also similar (their corresponding angles are the same measure, and the ratio between their corresponding sides is equal to 1). Similar and congruent.
As for the second graph (top right), they are not congruent since their corresponding sides are not the same measure. Furthermore, there is not a constant ratio between their sides, so they are not congruent or similar. Not similar, not congruent.
In graph 3 (bottom left), the two figures are not the same measure; therefore, they are not congruent. Nevertheless, notice that the sides of the larger triangle are 2 times the corresponding sides of the smaller triangle. The figures are similar. Not congruent, Yes similar.
Finally, graph 4 (bottom right) contains two circumferences that have the same radius. Therefore, the two figures are congruent and similar. Similar and congruent.