It is a rhombus
side
No, it is a conguent shape
It splits one side of the triangle into two congruent parts.
They are all congruent (equal length), parellel to another side, and perpendicular to another side
A square is the only shape to have 4 congruent sides.
If a triangle does not have the same length side as another triangle the sides are not congruent.
A rectangle
Not always but they may be similar in shape.
A transformation that produces a similar but not congruent shape is a dilation. In a dilation, a shape is resized either larger or smaller while maintaining its proportional dimensions, meaning the angles remain the same but the side lengths change. This results in a shape that is similar to the original but not congruent, as congruent shapes have identical sizes and dimensions.
Congruent Triangles have the same angles and side length measures
I'm not sure what a "congruent side shape" means. Every parallelogram must have two pair of congruent sides. That means two sides have equal length, and the other two sides also have equal length, but the two lengths don't have to be the same.
You have to prove that each side of one shape is congruent to the corresponding side of the second shape and that each angle of the first are congruent to the corresponding angles of the second. Sometimes this task is made simpler by the geometry of the shape in question. For example, with any regular polygons with the same number of sides, you only need to show that any side of one is congruent to any side of the other. The regularity takes care of the rest.