This document summarizes a guest lecture on analytics and metrics given by Darren Levy. The lecture covered: 1) Definitions of metrics and why they are important for measuring business performance and customer satisfaction. 2) What specific metrics to focus on, including vanity metrics to avoid and key startup metrics like CPA, ARPU, churn, and LTV. 3) Methods for collecting and optimizing metrics, including A/B testing, cohort analysis, and heatmaps. 4) Case studies demonstrating how Dollar Shave Club and Netflix used metrics and analytics to optimize pricing and content.