A quadrilateral is a shape with four sides.
A parallelogram is a quadrilateral where the opposite sides are parallel.
A rhombus is a parallelogram where all the sides happen to be the same size.
I learned these terms in school. Then I forgot all of them except for quadrilateral. Then, I Googled the others as a refresher for this blog post.
That being said...
The only times I've needed to recall these terms were on a test, in random conversation, and while watching game shows. (And this blog post...)
I know what a square looks like. I know what a diamond looks like.
I've never needed to classify them as quadrilaterals or rhombuses.
In fact, I can't even recall the last time I saw a rhombus-shaped object...except on a test that says, "What kind of shape is this?"
In school, I learned terms like parallelogram and rhombus, but I didn't learn how to cook, how taxes work, or what to do about my chromatic procrastination problem.
Complex terminology is perhaps good to learn as a cognitive exercise.
But in the end, it's most effective to focus and improve on the basics.