Ruby work this weekend

Working on ruby again. I picked the Beginning Ruby book back up again, and I started reading through the chapters. It such an easy language!!!

But, I'm reading through it, and I can't help but feel nervous that I'm going to forget everything that I'm learning in the book. I mean, it really is simple, and wouldn't need much to relearn, but man, I feel like I'm going to forget it all. Something as simple as iterators and loops has slipped my mind from when I started reading it (granted that was a couple of months ago). And I feel like using cheatsheets is...well cheating. And so would be using and IDE. I really want to commit these things to memory. But what are they that I want to commit to memory? It's hard to say right? What exactly do I want to commit to memory? what is essential for every programming language?

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I also opened the ruby ecommerce app again, but I couldn't get it to work at all. Gems. Gemfiles. Bundles. What are these things??? Why isn't there a good definition for us noobs??? Stack overflow!!!!!!