What's an Arduino?

Chapter 6 of Getting Started with Raspberry Pi talks about Arduino. I've never heard of this before, but it's apparently another small computer that can be hooked up to the Pi. They're framed as being complements of each other, but since I didn't know about it and I barely know my Pi (still in the box -- and will probably remain in the box until after Thanksgiving) I don't really understand the connection.

But this did make me think about the financial investment that I might end up making in the end. I've already decided that I'm not going to particularly stingy about what I buy, but that doesn't mean that I'm just going to buy absolutely everything. Here's what I have so far:

• CanaKit Raspberry Pi B+ Ultimate Starter Kit ($69.95): I went with the big kit because I don't have any electronics components to begin with. Starting with at least a somewhat reasonable collection of things like resistors, LEDs, and a breadboard seems like a good place to start if I'm going to actually make things.
• Raspberry Pi for Dummies ($15.08): I posted about the Dummies book in the first couple posts. Again, it's probably worth it for me even though much of the material is stuff that I either already knew or could have figured out on my own. However, there are also things I didn't know, plus it will probably be a reasonable reference moving forward.
• Getting started with Raspberry Pi ($11.35): This book is a bit more technical than I thought it would be, but it also seems to cover a broader range of programming ideas, which will probably help me out more after I've started to really wrap my mind around what's possible with the Pi (plus the Arduino).

I'll probably finish reading the book before I go to bed tonight. If not, I've got a wait at the airport and a plane ride on Wednesday. That should be more than enough time to get to the end.