It's a language model trained to return the most likely answer given a specific prompt. The goal of the answer is, to simulate a conversation and to sound realistic. ChatGPT is not grounded in reality, it does not know where its "knowledge" comes from, nor does it know whether the things it is saying are correct or wrong.

It can't tell it's wrong, it just reacts in a plausible well to you telling it it's wrong (acknowledging it and giving another explanation). Since ChatGPT is an expansion of GPT-3, those things won't be really solved since being somewhat of a knowledge base is a nice side effect, not the main goal of the model.