Asset, liability, and most owner/stockholder equity accounts are referred to as "permanent accounts" (or "real accounts"). Permanent accounts are not closed at the end of the accounting year; their balances are automatically carried forward to the next accounting year.
"Temporary accounts" (or "nominal accounts") include all of the revenue accounts, expense accounts, the owner drawing account, and the income summary account. Generally speaking, the balances in temporary accounts increase throughout the accounting year and are "zeroed out" and closed at the end of the accounting year.
Because the balances in the temporary accounts are transferred out of their respective accounts at the end of the accounting year, each temporary account will have a zero balance when the next accounting year begins. This means that the new accounting year starts with no revenue amounts, no expense amounts, and no amount in the drawing account.
By using many revenue accounts and a huge number of expense accounts, a company is certain to have easy access to detailed information on revenues and expenses throughout the year. This allows the management of the company to monitor the performance of all parts of the company. Once the accounting year has ended, the need to know the balances in these temporary accounts has also ended, so the accounts are closed out and reopened for the next accounting year with zero balances.