What is btw?

BTW

"BTW" is an initialism and internet slang abbreviation that stands for "by the way." It's commonly used in text messages, emails, online chats, and social media to add a tangential thought, provide additional information, or introduce a slightly off-topic remark. It is considered a form of internet slang.

Usage:

• Introducing a side note: "I'm going to the store later. BTW, do you need anything?"
• Adding an afterthought: "The meeting is tomorrow at 2 PM. BTW, bring your laptops."
• Changing the subject slightly: "I'm really enjoying this book. BTW, have you seen the new movie?"

It can also be used to soften potentially negative or controversial statements. Using "BTW" may signal that the speaker or writer isn't dwelling on the subject matter.