The name Tanakh is an acronym for the three divisions of the Hebrew Bible. They are the Torah, the Nevi'im, and the Ketuvim. The Torah includes the five Books of Moses: Genesis, Exodus, Leviticus, Numbers and Deuteronomy.
The Nevi'im ("Prophets") includes the books of the prophets: the former prophets in Joshua, Judges, Samuel, and Kings, and the latter prophets in Isaiah, Jeremiah, Ezekiel, and the 12 minor prophets (Hosea, Joel, Amos, Obadiah, Jonah, Micah, Nahum, Habakkuk, Zephaniah, Haggai, Zechariah and Malachi) combined into a single book.
The Ketuvim or "Writings" include three divisions: Psalms, Proverbs, and Job as a group, followed by a group of five that are the Song of Songs, Ruth, Lamentations, Ecclesiastes, and Esther. The final division contains Danuel, Ezra-Nehemiah, and Chronicles.
The middle division of the Ketuvim ties into several of the Hebrew festivals. The Song of Songs connects to Passover, Ruth to Shavuot, Lamentations to Tisha B'Av (which is like a Jewish Valentine's Day), Ecclesiastes to Sukkot, and Esther to Purim.
Because some of these are combined, the total number of books in the Hebrew Bible is 24. The Christian Old Testament breaks these up into 39 books. You can see the divisions and the different ordering of the books in the illustration. If it is illegible, you can see the original answer much more information about their differences here.
One Christian Bible, however, contained 48 books in its Old Testament. Truth be told, I use it for medieval research. I'll explain next time.
