1. Tread Blocks
We'll start off talking about tread blocks. These are going to be the main points of contact between your tires and the road. You'll notice larger tread blocks on more aggressive tires like mud tires because the terrain that a mud tire is designed for is a lot more demanding and needs as much contact with the ground as possible.
When looking at something like an all-terrain tire where it's designed more for comfort, there are often smaller tread blocks but more of them. This is because an all-terrain is designed to handle light off-roading while being comfortable and quiet on the road. The smaller tread blocks help with road noise and having more of them means that there is still plenty of rubber hitting the ground.
2. Tread Voids
Next, we'll cover tread voids. If you're not sure what this is, it's space between the tread blocks. Tread voids are designed to allow water, mud, and other road grime pass through the tire so you don't end up just gliding over a water patch on the road or constantly slipping in a mud hole. The tread voids also play a part in allowing the tire to bite into the terrain. You'll notice on a lot of tires, the tread voids are designed with a curve that swoops outwards towards the edge of the tire. This directs mud, rocks, and water away from the center of the tire. Some tires even have a groove that runs all the way around the tire that allows water to pass through during rainy conditions.
Siping is something that not a lot of people even know about and it's actually really cool! Sipes are the little lines that are cut into the top of the tread blocks. Often times you'll see them have a zig-zag shape and they're almost always super thin. The easiest way to understand how it works is to imagine yourself driving through a lot of snow. Snow is slippery, obviously, so how does siping help you traverse through the snow? Well, they are designed to grab tiny amounts of snow and hold it in the tire. This actually increases your traction in a winter environment. Pretty cool.
Sidewall plays a huge part in styling but also has a functional aspect as well. If you're new to off-road driving, you probably haven't heard of airing out your tires. This is when you let a good amount of air out of your tires before you tackle a tough obstacle, the thinking behind this is that if you air out your tires, you create a wider patch of rubber hitting the ground, this means you have more contact with the road beneath you, increasing grip.
Finally, we have styling. To many, the way a tire looks is almost as important as how it performs. Look around and check out all of the different tread and sidewall designs that manufacturers offer. Most of the design the tread to be functional rather than look good but sometimes this can create some pretty wild designs. Different types of tires also have a way different tread look. For example, a mud tire will look a lot more menacing than an all-terrain for both functional purposes as well as styling because they're designed for a hardcore off-roading build.