Before this lesson: make sure you've covered Nouns & Gender first.
A pronoun is a word that replaces a noun so you don't have to repeat it — like "he", "it", or "mine" in English. German has several types of pronouns, but as a beginner you only need to focus on a few of them right away.
Types you should know
das Personalpronomen
personal pronoun — I, you, he… (your A1 focus)
das Possessivpronomen
possessive pronoun — my, your, his…
das Reflexivpronomen
reflexive pronoun — myself, yourself…
das Demonstrativpronomen
demonstrative pronoun — this, that
das Interrogativpronomen
interrogative pronoun — who, what
das Relativpronomen
relative pronoun — who, which (later level)
das Indefinitpronomen
indefinite pronoun — someone, nothing
Memory trick: Most German pronoun names are just the English grammar word + "-pronomen" — Possessiv-pronomen (possessive), Reflexiv-pronomen (reflexive), Interrogativ-pronomen (interrogative). If you know the English term, you can usually guess the German one.