Economics is important for at least two reasons.
On the personal level, it is good to understand a little something about economics because economics teaches us about how we make decisions about what to do with our scarce time and money. It is good to understand, for example, the idea of weighing marginal benefits against marginal costs so that we can make informed decisions about what we should do in a given situation (like going to college versus taking a job right out of high school).
On the larger level, it is important to understand some economics so we can have some idea about what our government is trying to do. We should understand the basics of macroeconomics so we can have some ideas about, for example, whether the government should increase spending or cut it in our current situation. Understanding this makes us better, more informed citizens of our democracy.