That is simply a connector. It shows that a declarative clause forms part of a larger sentence.


That-clauses: functions

That-clauses can have various functions in sentences. A that-clause can be the subject.

It can be the complement.

Many verbs can have that-clauses as objects.

Many nouns and adjectives can be followed by that-clauses as complements.

Note that not all verbs, nouns or adjectives can be followed by that-clauses. For the structures that are possible after particular verbs, nouns and adjectives, see a good dictionary.

Preparatory it

In many cases, it is used as a preparatory subject or object for a that-clause.

The fact that

That-clauses cannot follow prepositions directly. We use the expression the fact that.