“My language is better because it has a strong type system!” screams Dave, your colleague developer, trying to push the programming language Cobol for the next micro-service of your company. Among developers, discussions about programming languages and their type systems can get quickly emotional. During these discussions, we often hear the words “type systems”, “data type”, “type inference”, “static typing”, “weak typing”, “coercion”, and more. The goal of this article is to see the meaning of all these words with examples, for you to have good foundations and understand the type system of your favorite programming language.