When a Rubyist hears "concurrency" they usually Google Elixir, Go, or even Node.js. Turns out, Ruby can be great for concurrency! The Global Interpreter Lock (GIL) does NOT prevent Ruby programs from performing concurrently. In this presentation we'll discuss the true meaning of concurrency, explore the inner-workings of the GIL, and gain a deeper understanding of how the GIL effects concurrent programs. Along the way we'll write a bunch of concurrent Ruby code, run it on multiple interpreters, and compare the results.