Load Path in Ruby - how it works? - Blog - Visuality

Recently, I encountered a weird Ruby error: Gem::LoadError: You have already activated X, but your Gemfile requires Y. A quick Stack Overflow search and a few commands with Bundler, and it was fixed. But it got me thinking: why did it happen in the first place? What does it even mean to activate a gem, and how may Ruby want to activate two gem versions at the same time? Let's search for answers together.