In English grammar, “there is” and “there are” are commonly used to indicate the existence or presence of something.
“There is” is used when the noun following it is singular. For example, “There is a book on the table.”
“There are” is used when the noun following it is plural. For example, “There are many books on the shelf.”
These phrases can be used in various tenses by adjusting the form of the verb “be”. For instance, you could say “There was a time when I was everything to you,” using the past tense. However, this usage is typically considered more advanced and may be classified as A2 level in some learning resources.