The Chart of Accounts is the basic setup component for an accounting system.  It is one of the first steps taken in the initial setup of an accounting software package (or manual accounting system if that is used).  The Chart of Accounts is essentially a series of code identifiers which are used to flag a particular accounting entry so the system knows where to put debits and credits.

A typical Chart of Accounts consists of:

Numerical Account Identifier
Account Name
Account Description
Account Group
Account Access Rules (users, debit/credit type)
Sub-Account Identifiers (for rollup or drilldown purposes)

For example: 1000500 - Cash Revenue - Cash taken at the register from customers - P&L Group - user 123, income revenue only - ID 1000501, 1000502, 1000503

The Chart of Accounts is typically broken into three major categories:

Income Statement (Profit & Loss)
Balance Sheet
Cash Flows

Within those major categories are typically a multitude of accounts for different purposes, the mix depending on the size, complexity, and industry of the business.