Sustainable management is a fancy way of saying "taking care of things so we can keep using them for a long time." Think of it like taking care of your toys so they don't break easily and you can play with them for a long time.
When we talk about sustainable management, we are usually talking about things in nature, like forests, oceans, and animals. We want to make sure that we don't use up all of the resources in these places and hurt them, because then they won't be there for us to use or enjoy in the future.
So, people who practice sustainable management make sure to use resources in a way that won't damage them or use them all up. They might make rules about how much of something we can take, like fishing only a certain number of fish or cutting down only some of the trees in a forest. They might also find ways to reuse things or make things last longer, so we don't have to keep using more and more resources.
By doing all of these things, people who practice sustainable management hope to make sure that we can keep using the things in nature for a long time, without hurting them or using them all up.