Existential clauses

Hello again.

I have a question about "existential senteces". My conlang Ayeri does
not make use of "to be" actually, although there is a verb "yomáo"
meaning "to be, to exist". This verb is thought for where you sometimes
read "EXIST" in the morphological breakdown of a sentence. But I still
haven't understood what the the difference betweeen "to be" and "EXIST"
is. It must have something to do with "existencial clauses" and
"equational clauses". I know that Spanish uses two kinds of "to be",
perhaps this is also for the distinction which I do not understand?

Thanks,
-- Carsten