Congruent shapes have the exact same size and shape. Drag the solid shape into its matching hole.
Rotate and flip the blue shape until it perfectly matches the gray target.
Similar shapes have the same shape but different sizes. Slide to dilate (scale) the shape to fit the outline.
Similar shapes have proportional sides. Tap the (+) to grow the height of the right triangle until it's similar to the left one.
You've mastered the basics of Congruence (same shape and size) and Similarity (same shape, proportional size).