Real User Monitoring (RUM) is a broad topic that means a lot of things to a lot of people. Broadly, what we're talking about is understanding our applications through the eyes of real users, with real browsers. By doing application performance monitoring with real users, we can have a full understanding of the performance, availability and functionality of our applications. We'll take a look at a number of core areas, including the web request lifecycle, synthetic vs. real user testing, and using summary metrics, histograms and logs for fun and profit.