Accounting is the act of computing something, usually by dealing with numbers. If you were very good at math in high school, you might think about going into accounting.
You can see the word count within accounting, which is one way to remember that the word has to do with keeping track of numbers — usually in relation to financial transactions. Balancing your checkbook is a form of accounting. Large firms often hire accountants to keep track of their earnings and spending. Accounting can also more generally mean explaining. Someone who decides to wear shorts to the prom is likely going to have some serious accounting to do!