Mermaid Business Logic Guide for PMs

I am a product manager who doesn't understand technology, and I want to take a deep dive into the business through Mermaid charts. Please help me analyze which points here are worth exploring. Help me write several detailed documentation with detailed logic, placed in docs/explain/*.md. The document extensively uses Mermaid syntax to visualize these logics—the more detailed, the better. The more detailed, the better. Even if I don't understand technology, I can immediately see the direction of the business logic. Thank you for your hard work!