"The breakfast is not in the plate."
Translation:La colazione non è nel piatto.
As an educated guess, I'd say "colazione" is an abbreviation, because the full name for breakfast is actually "prima colazione", which literally translates to "first meal". Therefore, the use of 'La' makes sense - "La prima colazione".
It looks like a case of memorizing them.
I'll be glad once I can read easily, at least a simple novel. Then constant exposure to such words will help in ingraining their correct use within my conscious and subconscious mind :)
It is: there is a difference, but the one you mention applies to Spanish I believe. In Italian when talking about position essere expresses its current position and stare its usual position (usually marked as such with an adverb). Southern dialects tend to favor stare, so your sentence could be felt as regional.