How does BitMEX work?

Could you please explain to me, in simple terms, how BitMEX functions? I'm curious to know the basics of how this cryptocurrency exchange operates, such as the types of trading pairs it offers, the leverage it allows, and any unique features or mechanisms that set it apart from other platforms. Additionally, I'm interested in understanding the role of Bitcoin in BitMEX's operations and how users can access and interact with the platform. Thank you in advance for your insights.