This document outlines 11 things that every .NET developer should know about Ruby. It provides a brief history of Ruby and its philosophy of prioritizing what feels natural over what is possible. It also summarizes key Ruby concepts like IRB, conventions, objects always being objects, blocks, dynamic typing, metaprogramming, and more. The document encourages .NET developers to try Ruby and notes some differences from .NET like how classes are open and types are deduced at runtime rather than compile time.