Proper forms of "There is" or "There are"
I need further education on how to properly use these.
I think that I can use есть, but is this not for definite purposes?
As in есть яблоко в доме. As in there is definitely an apple in the house?
Please correct me.
First of all, never begin a statement with "есть" - it sounds highly unnatural. You can put it in front in questions, particularly when you use it with "ли": Есть ли ...? - Is there ...? , but not in affirmative statements. (In general, beginning a Russian statement with a verb is a bad idea, unless you have a clear idea of what you are doing.)
Secondly, "есть" is used explicitly when you need to stress the existence of something - which is the same purpose for which you use "There is/are" in English, so your instinct is correct:
В доме есть яблоко = There is an apple in the house.
Note the word order in the Russian sentence. Яблоко is the last word since its existence is the new bit of information conveyed by this sentence: https://www.duolingo.com/comment/13955228
The direct translation for these is: There is and there are - "там есть".
But you never construct sentences this way in Russian. As stressed before, if you want to question the existence of a thing, you use: "Есть ли..."
If you want to check the existence in a specific place (here or there), you would normally use:
"Есть ли тут" (here)
"Есть ли там" (there)
"Есть ли на столе" (on the table)
If you want to state the existence of something, you can skip the verb. For instance, for something like "there are apples on the table", you can go with: "Яблоки на столе"
Please note that in Russian there is no difference between "There are apples on the table" and "Apples are on the table".
If you want to negate the existence of something, you can again skip the verb and optionally specify a place you're referring to: "(Тут/там/на столе) яблок нет"
You should keep in mind that in Russian, it is very often that the verb "to be" (быть) is skipped and is understood from the context.
В доме есть яблоко only means that "there is the/an apple in the/a house". It does not state that the existence of that apple is any more or less definite than in the english equivalent. Eg. "does God exist?" - "есть ли Бог?"