Because we hear about "the economy" in the news so often, many people have the misconception that economics is simply the study of business or making money. While this can be close to the truth in some cases, economics more broadly is a study of making decisions under conditions of scarcity, whether in terms of limited time, money, or other resources. Economics encompasses everything from the microeconomics of a personal decision about grocery shopping to the macroeconomics concepts used to describe the aggregated decision-making of entire populations.
Indeed, economics has many useful concepts that we can use to better understand how we approach various decisions in our daily lives, regardless of whether money is involved. The concept of "opportunity cost" describes the lost gains from one alternative that we sacrifice when we choose another; for example, if you decide to major in economics, one opportunity cost is losing the ability to major in engineering instead.
Of course, the ability of economics to explain and predict decision-making is particularly powerful in the realm of business. The concept of "competitive advantage," for example, guides companies to focus their business on products and services that they can provide either at a lower cost or with a higher value than their competitors. This is still a core concept for entrepreneurs, who must clearly define their competitive advantage as well as their strategy for preserving it to raise funding from venture capital or other investors.
The myriad applications of economic thought have led to the creation of many more specific subfields, such as project economics, behavioral economics, environmental economics, and others. But at the end of the day, they are all united by a focus on decision-making with constraints - regardless of what the limited resources are.