There are many levels of 'not understanding'. Few people understand Quantum Theory; most people understand that water is wet. Why must you label them? Help them understand, and if for whatever reason they are not interested, move on. If you need a label, try uninformed, unaware, naive...
A person who understands everything is often referred to as omniscient or all-knowing.
Smart
A person who speaks and understands many languages can be called a polyglot.
A soul mate...
Some one who values friendship could be called best friend. Such a person understands the true meaning of friendship.
someone they can trust, someone they cant live without, someone who understands them :)
not me pls someone should help me
you rephrase your question so that someone understands it.
The DJ understands his audience and responds accordingly.
Printer Control language
yes, i do!! finally someone understands me!!
A food connoisseur is someone who likes, understands and knows a lot about food.