Just read the prologue to understand. All I can put here is that it’s a time machine.

A character from the game show Double Down. Personality: Bookmark is a delicate girl who is soft-spoken and introverted, but isn't afraid to speak her mind or put others in their place when push comes to shove. She tends to read most of the time and tries to avoid engaging in social activities. Her original label suggests that she's kind-hearted, meaning that she has a friendly and sympathetic nature. Personality definitely not copied from the Wiki.

You’re Baljeet. Buford sometimes gets along with you, but he’s a bully, so not all the time.