Depreciation Expense is a temporary account since it is an income statement account. As a temporary account, Depreciation Expense will begin each accounting year with a zero balance and will have its balance at the end of the year closed to an equity account such as retained earnings or a proprietor's capital account.
On the other hand, the balance sheet account Accumulated Depreciation is not a temporary account. Accumulated Depreciation is a contra asset account and its balance is not closed at the end of each accounting period. As a result, Accumulated Depreciation is a viewed as a permanent account.