Okay kiddo, do you know there are two important books in the history of Christianity: the Hebrew Bible and the New Testament? The Hebrew Bible is an old book, and the New Testament is a newer one. The Hebrew Bible is also called the Old Testament by Christians.
Now, the New Testament talks about a man named Jesus, who Christians believe was a very special person. Some parts of the New Testament mention things that were written in the Hebrew Bible. These things are called 'quotations'.
It's kind of like when I tell you a story, and I say something like "as my grandfather used to say..." - I'm quoting my grandfather. In the same way, the writers of the New Testament sometimes quoted things that were written in the Hebrew Bible.
For example, you know the story of David and Goliath? In the Hebrew Bible, it tells how David killed Goliath, the big, mean warrior. In the New Testament, a man called Paul talks about David and says, "as it is written in the book of Psalms..."
So, the writers of the New Testament were very familiar with the Hebrew Bible, and they used it to help describe who Jesus was and what he did. And when they used words directly from the Hebrew Bible, it helped to show that Jesus was connected to the history and stories of the Jewish people.