It's used like sweating. We lose heat by havibg water evaporate off our skin. Right now get warm water and put it on your arm, then blow on it. It gets cold until it is fully evaporated. For water to change from the liquid to the gaseeous phase it needs energy. Think like water molecules are holding hands in a liquid. If one of them wants to come free and fly through the air it needs to somehow get the energy to break free from the grip of the others first. When water evaporates from your arm it tales this energy in the form of heat. It turns heat and uses it to get to the gaseous phase. As long as there is water on your arm it can be cooled that way.

That's what data centers do as well. They take water to cool their processors and the let part of it evaporate into the air. That way the parts of the water that remain are like your arm - the get cool quickly.

It's very effective. But if you live in a small town and next door there's a massive datacenter that takes out all the groundwater and basically just boils it until it disappears, you might get angry after a while.

They use evaporative cooling for a chiller plant most likely.

What I don't get is how the water is "consumed", it's not like it's gone right? It evaporates and then just comes back down as rain surely?

Same with water consumption of a sweater or a steak.

There probably is some good reason for measuring it like that but conceptually I don't get it.

To add to what others said, it’s a tradeoff.

Your gaming PC not only runs up your electric bill from the wall, but the AC as well. It has to work to get all that heat out.

This is the equivalent of water cooling your PC, and piping it to a hot tub outside. It would heat it and evaporate water faster, but it’s basically free and uses basically no electricity.

That’s the tradeoff. It’s water evaporation instead of heat pumps. It’s trading water usage for lots of electricity usage, which in some cases, is well worth it.

And what if you live in a cold climate, you say? Well, evaporative cooling is most cost efficient in hot and (ironically) dry climates.

Server farms use water to cool computers, it's like water called computers but on a bigger scale

Aircons condense water from the atmosphere the same way water on your shower mirror happens because the mirror is colder than the fog

If you're familiar with condensation and the rain cycle it should help you understand further

taps the fact that electricity is a steam reaction and even if you don't see it, the electricity you're using is made by decompressing water into vapor, whether by burning coal through turbines/boiled wind from water sources creating wind power/ even nuclear reactors are often a boiling water reaction going through turbines, creating a net loss of 'water' if we don't have natural condensation utilities to convert 'air'

At this point, I wouldn't be surprised if it turned out that they're destroying the environment on purpose for some nefarious purpose. e.g. maybe they think it's easier to rule the masses if natural ressources are very scarce.