Sure. The Ising Model is a model in physics that describes (among other things) the process by which materials acquire a large-scale magnetic moment. It turns out that it actually can describe a lot of other diverse sorts of phenomena--among other things the formation of social consensus, at least under certain conditions. More specifically, it turns out to be a pretty good model of what physicists call phase changes: transitions from one "kind" of state to another. Think of the transition of water from liquid to gas when you heat it, or the transition of an iron rod from being non-magnetized to magnetized when you run another magnet along its surface. Those are phase changes.

What the Ising model looks like is easiest to grok when it comes to magnets, but for the model to make sense you have to know a little bit about how (fucking) magnets work. Almost every object has a magnetic field. Ordinary objects--that is, objects that we don't tend to think of as "magnets"--just have very weak and disordered magnetic fields. When you (say) put your hand flat on your desk, the force by which the desk "pushes back" on your palm is mediated by the electromagnetic force. What separates that kind of interaction from the sort of interaction in which (for instance) a refrigerator magnet seems to exert a force "at a distance" on a piece of iron is not the presence of a magnetic field, but rather the strength of the field.

On a quantum mechanical level, magnetic fields are generated by a property called "spin." You can think of this as being roughly analogous to angular momentum in macroscopic objects--think of something like a baseball or billiard ball given "front spin" or "back spin." The "direction" of spin for quantum mechanical objects generates a very small (that is, very weak and short range) magnetic field. In most ordinary objects, all these fields "point" in different directions, because the spins of the particles aren't correlated with each other in any meaningful way--this particle over here is spinning in one direction, while its neighbor is spinning in a different direction, and so on. Because of this lack of correlation between individual particles' spins, the overall magnetic field--what you get when you "add up" all the little tiny magnetic fields of the quantum mechanical particles--isn't very strong. You have to get right up close to feel it. However, when all (or very many) of the spins start pointing in the same direction, the small fields no longer cancel each other out. Instead, they start reinforcing one another creating a stronger and stronger field until it's significant enough to feel when you're holding the magnet a few inches away from your fridge.

So how do we get from the "random" spin situation to the "coordinated" spin situation? This is where the Ising model comes in. You can picture some object--say, a chunk of iron--as a big grid (or lattice). Each of the particles making up the chunk of iron is represented by one point on the grid. Each of those boxes might have a bunch of interesting properties, but what we care about right now is magnetism, so we'll represent a particle that's spinning "overhand" with an up arrow, and one that's spinning "underhand" with a down arrow. The result will look something like this.. The spins in that picture are distributed more or less at random, so we don't have much of an overall magnetic field. How do we get one? Well, we have to get all of the spins "pointed" in the same direction. There are (at least) two ways that can happen: via the application of an external magnetic field that's so strong it "pulls" all the spins into alignment with it, or spontaneously. The former is what's happening when you magnetize a nail by running another magnet along it; the latter is how natural magnets like lodestones form, and it's the more interesting option for our purposes.

If you look at the image again, you'll notice that while the ups and downs are distributed at random, you still end up with a few "chunks" of ups and downs right next to each other; this is bound to happen with a random distribution (this is a kind of symmetry breaking , which is another thread you can follow into a wide variety of topics). Now think about what happens if each point on the lattice has a small (but non-zero) effect on its neighbors: if I'm an up arrow and I'm surrounded by a random assortment of ups and downs, I'll just keep being an up arrow. On the other hand, if I'm an up arrow surrounded by a sea of down arrows, I'm going to have a tendency to "flip" and become a down arrow myself, since all those down-arrow neighbors are producing small "downward pointing" magnetic fields of their own. If the coupling between neighbors is strong enough, this can result in all the arrows in the whole lattice influencing each other to point in the same direction, which will cause the object to spontaneously magnetize itself without the need for an external magnetic field. It can also mean that the exact shape of the initial random distribution--where the random collections of ups and downs start out--can strongly influence how the final situation shakes out; if there just happen to be a few more clusters of ups, then you might end up with no down arrows at all, and vise versa. Most importantly for our purposes, you get the appearance of coordinated, goal-directed behavior without any central authority at all. The orderliness of the phase transition just "falls out" of the dynamics of the system combined with its initial state.

It turns out that this is a super flexible model in general. Any kind of system with elements that have limited range interactions with other nearby elements and influence those neighbors to become correlated with themselves can be modeled as an Ising-type system. Superconductivity works like this. Bird flocking works like this. Lots of social interactions work like this. Your views about politics don't have an influence over the views of everyone everywhere, but they do have an influence over your "social neighbors"--that is, the people you interact with on a regular basis. If you're hanging out with a bunch of people who are more radical than you are, you're going to have a tendency to radicalize as well. This helps us model how things like the alt-right emerge, and what role social media might play in those sorts of "consensus shifting" social events.

In the case the OP was talking about above, the sudden banning of leftwing spaces looks like a coordinated action, and it is in some sense--just not one that requires any central authority or directive. Instead, all of the big social media companies look at what their neighbors are doing, and adjust their behavior to be slightly more like the average of what they see. That sort of dynamic is very conducive to sudden phase changes: situations in which a small ripple quickly amplifies itself into a tidal wave of difference, and the flock of birds suddenly turns without any one bird making the decision to shift directions.