Microeconomic theory studies decision-making based on costs vs. benefits. It's really that simple! Of course, throughout this neoclassical (i.e., microeconomic) theory, you'll study many details, including many graphs, but try not to let that confuse or discourage you --- this course studies costs and benefits (from a few different perspectives) and ultimately, the resulting, rational choices.
So, lets start at the very beginning and make a list of exactly what the core assumptions are:
1. Assume scarcity.
2. Scarcity creates a need for decision-making (i.e., choices).
3. Choices involve opportunity costs (i.e., sacrifices).
4. Assume that people are rational.
5. Consumers act to maximize utility subject to budget constraints.
6. Firms act to maximize profit subject to cost constraints.
7. A free market allows both consumer and producer choices to end up in equilibrium.
..... there are more assumptions to follow, but this is a good start.
