What is Basic Attention Token (BAT)?

Could you please elaborate on what Basic Attention Token (BAT) is? I've heard it mentioned in the cryptocurrency and digital advertising space, but I'm not entirely sure how it works. Is it a form of payment? A reward system? Or does it serve a different purpose entirely? I'm curious to understand its core functionality and how it aims to revolutionize the digital advertising landscape. Additionally, I'd like to know if it's widely adopted and if there are any significant partnerships or integrations that have been established with BAT. Thank you for your assistance in clarifying this topic.