This is the 17th most frequent German word.
das
"The" (definite article, neuter) or "that/this" (demonstrative pronoun).
Here, 'das' is used as a demonstrative pronoun meaning 'that'.
Das ist mein Haus.
That is my house.
In this sentence, 'das' is a definite article used with a neuter noun, 'Auto'.
Das Auto ist blau.
The car is blue.
In this example, 'das' is a relative pronoun referring to something previously mentioned.