Decision-making is the work of making important choices, especially in a company, a school, or a government. It names the process, not the person. You will hear “decision-making process”, “decision-making power”, and “poor decision-making”. It is office and textbook English, hyphenated, and a little stiff for talking about what to cook tonight — for that, people just say “deciding”. Though actually, a lot of “decision-making” in big organisations is slow, shared, and political; the tidy word hides how messy the real meetings can be.