If one shape can become another using Resizing (also called dilation, contraction, compression, enlargement or even expansion), then the shapes are Similar...
Sometimes it can be hard to see if two shapes are Similar, because you may need to turn, flip or slide one shape as well as resizing it.
When two shapes are similar, then:
corresponding angles are equal and the lines are in proportion.
If one shape can become another using Turns, Flips and/or Slides, then the shapes are Congruent...
The two shapes need to be the same size to be congruent.When we need to resize one shape to make it the same as the other, the shapes are Similar.
In Summarized;When we RESIZED a shape,it is similar.When REFLECT,TRANSLATE or REFLECT,it is congruent.
Hope it Help:)