Accounting
Accounting is the process of keeping track of business transactions, both internal to a company, and external transactions with customers and suppliers, and also to create any reports required by government agencies, such as the IRS or SEC.
People who perform this task are called accountants, who are usually certified, and frequently employ bookkeepers to perform the more mundane tasks of data entry.
For millennia, accounting has employed what is called "double entry bookkeeping", in which every transaction is entered in two ledgers, increasing one and decreasing the other. This allows for "balancing" the accounts, which helps reduce errors.
While accounting used to be done by hand, on paper, it is almost always done using computer programs today.