"The bread is on the plate."
Translation:Хлеб на тарелке.
"В" means "in". "На" is used for "on".
In this case, "на тарелке" means "on the plate".
We only use "есть" in specific constructions (like possession - I have a plate - У меня есть тарелка) and situations where unusual emphasis is placed on the existence or nature of something.
Why do you say «Хлеб на тарелке» when you say «В тарелка вода»? I'm not asking about the word order, but why is bread on the plate while water is in the plate?
Bread is kind of solid, and it can be placed on top of any plate even if it is completely flat. Water is liquid, and it can only be inside the plate or bowl.
Can someone explain when is it тарелка and when is it тарелке? Is it a declination?
It is, it's a declination for the prellsitional case, you usually change the last letter to be an е for this case (with some exceptions line when the word ends in и then you add a second и)