As the PM for Facebook Profile, understanding and measuring success would involve a combination of quantitative and qualitative metrics. Firstly, I would look at user engagement metrics such as daily active users, time spent on the platform, and frequency of profile updates. These metrics would help me understand how much users are interacting with the platform and how often they are doing so. Secondly, I would also focus on user satisfaction metrics such as user retention rate, Net Promoter Score (NPS), and user feedback. These metrics would help me understand how satisfied users are with the platform and identify areas that need improvement. Thirdly, I would also consider business metrics such as revenue generated from advertising on the platform, user acquisition cost, and customer lifetime value. These metrics would help me understand the financial impact of the platform and identify opportunities for growth. Ultimately, the success of Facebook Profile would be measured by its ability to meet the needs and expectations of its users while also driving business growth. By monitoring a combination of user engagement, satisfaction, and business metrics, I would be able to continuously iterate and improve the platform to ensure its success.