As you may know by now, based on your textbook, Economics is the science and the study of how people allocate their limited resources to satisfy their unlimited wants. The ultimate purpose of economics is to explain how people make choices.
"How do people decide how much to work?" Time is scarce resource you may know this very well as a student. There's just not enough time to do everything we'd like to do. How do we decide how much of our time to spend working? There's a tradeoff: the more time we spend working, the higher our income, and therefore the more stuff we can buy. But, the more time we spend working, the less time we have for leisure - hanging out with friends, going hiking, watching movies, etc.
"How do firms decide what kind of labor to hire?" Firms can hire unskilled or skilled workers. The skilled workers are more productive, but cost more than the unskilled workers.
Decision-making is at the heart of economics. The individual must decide how much to save for retirement, how much to spend on different goods and services, how many hours a week to work. The firm must decide how much to produce, what kind of labor to hire. Society as a whole must decide how much to spend on national defense ("guns") versus how much to spend on consumer goods ("butter"). As you can see Economics helps to answer numerous of very important questions.
How you decide how much time to spend working? "How do firms decide how much to produce?" If there's a lot of demand for the product, what does that mean for the price that firms can get for the product?