Avinash Kaushik, analytics evangelist for Google and a cofounder of Market Motive, always provides food for thought in his blogs. Here's an immense one, posted on Avinash's blog site, Occam's Razor. It's a far-ranging examination of seemingly “simple” things, like "What is the difference between a metric and a key performance indicator (KPI)?" "What is a dimension in analytics?" "What is segmentation?" "Are goals metrics?" And many more.