Standard language ideology refers to the belief or idea that there is a certain way of speaking that is considered "correct" or "proper", and that this way of speaking should be the norm in society.
Think about how your teacher might correct you when you say "ain't" or use slang or regional dialect in your language. This is an example of standard language ideology. People may judge or look down on those who don't follow these "correct" language rules or speak in a non-standard way.
This ideology often relates to the idea that there is a hierarchy of languages or dialects, where some languages or dialects are more prestigious or superior to others. For example, someone might think that speaking English with a British accent is more prestigious than speaking English with a Southern American accent.
It's important to note that this ideology can exclude and marginalize people who do not follow this standard, and can perpetuate social inequality.