Detailed explanation
Existential there introduces the existence, presence or occurrence of something that is new to the discourse. It occupies the grammatical subject position, while the notional subject follows the verb: There is a problem. There were several objections. The structure allows the writer to present new information gradually instead of beginning with a long or unfamiliar noun phrase.
In careful formal English, the verb generally agrees with the following noun phrase: There is one remaining issue; there are several remaining issues. In informal speech, singular there’s often appears before a plural noun, but this is usually avoided in edited academic or professional writing. With coordinated noun phrases, agreement may follow the nearest noun in speech, but formal prose is clearer when the sentence is recast if the pattern feels unstable.
Advanced forms combine there with modal, perfect, progressive and passive verb phrases: There may be a delay. There has been a misunderstanding. There appear to be several inconsistencies. There are believed to be significant regional differences. The verb following there carries tense and agreement, while be, appear, seem, remain and exist help express certainty, persistence or appearance.
Existential there differs from the place adverb there. In “There is a file on the desk”, the first word is existential and does not refer to a location. In “The file is there”, there is a place adverb. Pronunciation also differs in natural speech, but the grammatical test is whether the sentence introduces the existence of something.
Do not use existential there when the noun phrase is already the established topic and a direct subject would be clearer. “The report contains three recommendations” may be stronger than “There are three recommendations in the report” when the report is already under discussion. Choose the structure according to information flow: existential there is particularly useful when introducing a new entity, problem, trend or possibility.
How to form it
Use there + finite verb + notional subject: There is a concern; There are concerns. Advanced patterns include there may be, there has/have been, there appears/appear to be, there remains/remain, and there is/are believed to be. In formal writing, make the finite verb agree with the following noun phrase.