Diglossia

Diglossia is like having two different languages that people use in different situations. It’s like having one language that you use with your family and friends at home, and another language that you use at school or work.

For example, in some countries, people might speak one language at home and in everyday conversations (often called the “vernacular” language), but they also learn a more “formal” or “standard” language in school or for official purposes, such as in government documents or in the media. In these places, both languages are considered important and valued, but they serve different purposes.

So, diglossia means that in some cultures and societies, people use different language varieties for different purposes or social situations, and these varieties are not necessarily considered "better" or "worse" than each other, but they serve different functions.