There is and there are [there exists etc.] are called existential sentences or utterances. There is called a dummy subject.
There are apples on the table.
There is at least one entire book on the subject: Existential Sentences in English (RLE Linguistics D: English Linguistics) 1st Edition by Gary L. Milsark (Author)
In English grammar, an existential sentence is a sentence that asserts the existence or nonexistence of something. For this purpose, English relies on constructions introduced by There (known as the "existential there").
From David Crystal's, Making Sense of Grammar. Pearson Longman, 2004
The term existential sentence is an attempt to capture the meaning conveyed by the following type of construction:
- There's a strange cat in the garden
There were lots of people in town.
There weren't any apples on the tree.
There appeared a bright star in the sky.
The word there comes first . . .. It is then followed by the simple present or past tense of be, or a small range of 'presentational' verbs, such as: appear, arise, ascend, come, emerge, erupt, exist, float, occur, spring up, stand. The noun phrase following the verb is usually indefinite, as shown by such words as a and any. . . .
