I know what you're thinking. I thought it too when I first heard the term. "Raspberry pie? I love raspberry pie! But what does it have to do with our greenhouse?" Let me tell you, I was very disappointed when I found out what it really was.
First of all, the pi in the name is short for Python, the code language they normally use for the pi, not pie like the food. A raspberry pi is a tiny computer, about the size of a credit card. It can do a lot of things a regular computer does, like browsing the internet, playing games, and programming, which is what we will be using them for. They're also practical for projects like ours, because they only cost $5-$35, depending on the pi.
The reason for the creation of the raspberry pi was to teach kids how to program computers and understand how to use code to automate and create, as well as making them affordable so they could be used in 3rd world countries. With the importance of technology in society today, this skill is more prevalent than ever. The raspberry pi requires an SD card, a USB power source, and a connection to a keyboard and monitor. You can also add modules like cameras, microphones, touchscreens, and more, if you're willing to pay the $20-$30 dollars extra for them.
The raspberry pi is quite confusing if you aren't familiar with coding or its uses. Here's the most important things to remember: it is basically a small computer, it's inexpensive, it runs on a code language called python, and can have modules like touchscreens, cameras, webcams, and microphones installed depending on what you want to use it for.
Still don't understand, but really want to? Check out these websites that I found really helpful! http://www.makeuseof.com/tag/9-things-wanted-know-raspberry-pi/ https://opensource.com/resources/what-raspberry-pi
Or, if you want it directly from the source, or are interested in purchasing a raspberry pi, here's the official website: https://www.raspberrypi.org/