DISCLAIMER: A little bit of Minecraft base game knowledge will probably be needed to fully understand this guide!
This is a guide for a specific game mechanic, not the full game, after all.
Go, my noble steed!
Unless you've been living in a cave your whole life, you've probably played or at least heard of Minecraft, a game where you can live in a cave your whole life. Known for its limitless potential for creativity, Minecraft allows you to do just about anything, from building a 17-story castle out of dirt, to riding a pig on a saddle, to making an effective method of transportation via building a pathway of ice through literal Hell.
There's nothing in this game you can't do. One iconic feature in the game, almost as old as the game itself, allows you to build technical contraptions to your heart's extent. That feature, of course, is the focus of this site- redstone.
Fig. 1: Example of a simple redstone contraption
Fig. 2: A signal strength of 15 carries a signal for 15 blocks. Notice how signal strength is represented in the redstone dust via a gradient.
Good question. As someone who has been playing Minecraft for 11 years, most of my life, even I was asking the same question until just recently.
Redstone is not intuitive. There's little to no hints in the game as to what it is or how it works. Minecraft is just kind of just like that sometimes, and it doesn't help that redstone happens to be one of Minecraft's most complicated mechanics. Most Minecraft players are understandably in the dark.
So, let's start with the basics. Redstone is, simply put, electricity. Its basic function is to "power" certain blocks and components, giving them two states: on and off. Everything else is built off of this simple binary.
It's difficult to explain further without an example of a simple redstone contraption. In Figure 1, you'll see three redstone components (blocks/items useful for working with redstone) interacting with each other to create an output. In this case, the lever is powering the redstone dust, which is in turn powering the redstone lamp. The redstone dust acts as the wiring, carrying the signal from the lever to the lamp. Once we flip the lever to Off, the redstone dust becomes unlit, and so does the lamp.
Now that we know the simple On/Off functionality of redstone, it's important to note another vital aspect known as "signal strength." A redstone source component, such as a lever, will always output a signal strength of 15, the maximum possible value. What does this mean? Well, if that line of redstone dust on the left half of Figure 1 was extended to 16 blocks long, the redstone lamp would not power on. Signal strength represents how many blocks a redstone signal can be carried via redstone dust. In Figure 2, this scenario is laid out. Some redstone components will output different signal strengths based on a multitude of different variables- but we'll get into that later.
The stone and deepslate variants of redstone ore. Deepslate, the much more common of the two, can be found... deeper.. in caves.
Witch blood...?
I was out for a walk in my backyard and I found some! But my stone pickaxe just won't do...
Redstone can be found in that cave you've been living in. It's only obtainable via mining redstone ore (or as a drop from a witch, for some reason?). You're gonna have to dig down pretty far though, as it can only be found below Y-level 15 and gradually increases in rate the further down you go.
Once you find some ore, be sure to mine it with a iron pickaxe or better, and it'll drop redstone dust- the lifeblood of all things redstone. Redstone dust, while useful on its own, can also be used as an ingredient to craft many redstone components.
Congrats, you've found redstone! We know a little bit about how to use it, but in reality, we've just scratched the surface...