"There is an egg on the plate."
Translation:Na talerzu jest jajko.
Yeah, you could say that, although "Na czym jest jajko?" is an unusual question. "Gdzie jest jajko?" would be more probable.
Anyway, in "Na talerzu jest jajko", the existence of the egg is a new piece of information. In "Jajko jest na talerzu", you already start with the knowledge that there is some egg. This is also visible in English in this example: "There is an egg on the plate" vs "The egg is on the plate". But often you have a situation when in Polish you have two or more quite different sentences while you would translate them the same into English.
On its own - perfect sense, but it's not exactly a translation. Your sentence starts with the knowledge that there is some egg and says where it is located. Here we start with the plate and say what's on it.
I see that "Jajko jest na talerzu" is accepted... I don't think it should be. Removed now.
Added "Na talerzu leży jajko".