Ask HN: What is the difference between a junior and senior developer?

I'm about to graduate from college and have been contemplating about this question a lot lately, especially in regards to specific languages/frameworks (ruby/rails in my case)

I know that I'm not that most raw-engineering talented, but I believe I have dabbled a lot with web development (full-stack and again, Rails) that should give me a significant competitive advantage, so i was curious:

How do you specify/categorize junior/senior developers? Is it production-experience, language/framework knowledge, knowing best-practices or just raw engineering talent?