This sounds like a simple question, but it's actually surprisingly complicated. We often think of vitamins and minerals as one (or two) related categories of organic chemicals, but it's actually just a label that we give to a wide variety of chemicals that get used in a vast number of different, often unrelated biochemical processes. It's even more complicated by the fact that we include structurally distinct chemicals, like Vitamin D, under the label of "vitamin" when it's more accurately called a hormone. But it really is complicated to explain how they work, since they're so different from each other. vitamin K, for example, is a chemical that the body requires in the process of producing blood clots. It would take more space than is available here to explain that biochemical process, but even if you knew the details of it, that wouldn't make you understand how vitamin B12 helps energy metabolism, or how sodium helps regulate electrical charges for muscle contraction. There's whole books on this stuff that barely scratch the surface of the organic chemistry knowledge that can be understood on how they work. But I recommend at least having a basic knowledge of what vitamins/minerals are often short in the type of diet you eat (or the population where you live), what food sources you can get more from, and signs of deficiencies. That info is all over the internet.