Just one last quick note: people use "ام" "ی" "ایم" "اید "اند" in these sort of sentences, preferably. I mean instead of using «هست»'s conjugations, it's better to write or say it this way "ما انسان ایم". To wrap it up: You rarely need to use «هست» in its singular form (Just when you are talking about existence of something you MUST use it) use mostly see «است». And for plural or other singular forms of «است». You have to use «هست»'s conjugations even when you need a linking verb in this can it has not the meaning of existence anymore (most of the time!)

But the differences between «هست» and «است» are more delicate and complicated! I'd try to give you some criteria but it might seem confusing somehow in spite of my intent! first off, the central difference is: «است» is a "linking verb" but «هست» is not (it's independent). I mean you can use «هست» with a subject sometimes and the sentence would be completely correct (A two-word sentence) but you almost never ever can use «است» with a subject. In this usage «هست» means "exist. You can translate it as "there is" or "there are" in English. Examples : "خدا هست" means "there is God" or "God exists" but "خدا است" is an incomplete phrase and meaningless! 1) «هست» is used when you want to talk about "existence" of something and «است» when you're going to talk about "quality" of something or "describing" it or giving some "information" about it. Examples: "خورشید هست" means "the sun exists" or "there is the sun" " خورشید زیبا است" means "The sun is beautiful". 2) There is no conjugation for «است». it means this verb only use and exists as singular (In Iranian Persian). But the question is, what should we do when we're going to use «است» as a linking verb but in another conjugation? The answer is: you have to conjugate «هست» and use it in this case!! Examples: "ما هستیم" means "we exist" or "we're here" But when we want to say "we are humans" although we need a linking verb here but since we can not conjugate «است», so we should say " ما انسان هستیم". It's the same for other conjugations.

There is no difference in meaning Between «می‌باشد» and «است». The only difference is that we never use «می‌باشد» in spoken Persian. (That's one of the reasons you're not allowed to use it in writing. But some people do so in order to pretend that their text or essay is a bit formal!! That's why you only find it in commercials and rather official documents or transcripts). In brief, You ALWAYS can replace «می‌باشد» with «است» and read the sentence without any difficulty! Just one another note: Be aware of plural form: «می‌باشند», because there is no plural form of «است». So if you want to edit a sentence and put the correct form of «است» instead of «می‌باشند» you must use «هستند» !!