Economics is about making choices in the face of unlimited wants and limited resources. Economists study the choices humans make. Why they make certain choices, what they hope to gain from the choice and how much they give up each time they choose.
We are forced to make choices in our daily lives because not all our wants can be satisfied with the available resources. When we make choices, we have to give up something else.
Now, let us try to understand the difference between financial costs and economic costs.