Not wasting, and/or not destroying.
When the average person hears this word they think of trees and birds and wildflowers, and maybe that nice brook they once saw a picture of, and then they think of not destroying them.
Some call it preservation, thinking that with conservation you get to use things up until they're gone, and it's all right as long as it happens slowly. These people get hopping mad if you say "conservation" and what you really mean is "not using it up, ever".
One way or another, things change, and if they don't get consumed they'll likely rust or rot or get bulldozed some day, although it would be better if they didn't.
Conservation seems to make most sense in the context of using wisely what we have to use, and acknowledging that there are things too precious or rare to be consumed. Period. Call it what you will.
Backpackers are practical folk who prefer to amble about wooded hills and other unspoiled territory. But they realize that back home they still have to make a living.
Given that, they practice utilitarian conservation by necessity. As in conservation of fuel, conservation of water, conservation of food, conservation of clean clothes, conservation of batteries, matches, sunscreen, toothpaste, and all the rest.
Since a backpacker has to carry everything, a backpacker learns to conserve on expectations. "Take what you need and only what you need" is a good rule. When fuel is burned, water is drunk, food is eaten, soap is gone, the last drop of sunscreen spread on tender skin, that's it. You don't get no more.
Backpackers learn this first-hand.
The ones that come home again. They get smart by experience, and they make things work. It's good training for a long life on spaceship Earth, which is swarming with idiots who don't know any of this.