As usual, we start with the definition. The numeral is a part of speech that denotes a NUMBER, as we may guess from the name.
In the course we encounter them at the very outset, in Lesson 3. Let me remind you that Soroka works on the principle of a phrasebook, thus, we study ready-made phrases and learn how to apply them in speech. In Lesson 3 we talk about age, so ordinal numerals or numbers are needed to define it.