Ask HN: Help me be a better CEO - I need to learn the tech.

I've read repeatedly on HN that a CEO must at least be familiar with every aspect of his or her business and I thoroughly agree.

I've been running my startup for over a year now and handling everything but the tech aspect pretty well (hired a developer). Now I'd like to gain an understanding of the technical aspect of things to the point where I can at least understand how much work a feature request translates to.

The web app is built on Rails, Javascript, HTML and CSS. Sorry if any part of that was redundant.

I'd like thoughts from hackers on where to start with learning how to code for a web application. I know there's a lot of languages and options out there depending on what I want to do so I hope I've made my end goals clear. I'd also like to understand the interplay between Ruby, Ruby on Rails, PHP, Javascript, etc. I literally know next to nothing about the technical aspect of it and I want to change that.

What language should I start with, knowing my goals? What specific resources would you suggest for this (paid, free, anything)?

Thanks in advance for your help.