Differentiate between depreciation expense and accumulated depreciation, including how these accounts are classified (which elements) and where they appear in the financial statements.

Depreciation Expense and Accumulated Depreciation are two concepts related to the accounting of fixed assets, but they have different meanings and roles in financial statements.

1. Depreciation Expense: This is the portion of the cost of a company's fixed assets that is considered used up in a particular accounting period (usually a year). It is an expense and therefore reduces the company's net income. It is classified as an operating expense and appears on the income statement. The depreciation expense is calculated based on the cost of the asset and its useful life.

2. Accumulated Depreciation: This is the total amount of depreciation that has been charged against a fixed asset from the time it was put into use to the present moment. It is a contra asset account – meaning it is paired with and reduces the value of the related asset account (in this case, fixed assets). It is classified as a long-term asset and appears on the balance sheet. Accumulated depreciation increases over time as more depreciation expense is charged against the asset.

In summary, depreciation expense reflects the cost of using the asset in a particular period and reduces net income, while accumulated depreciation shows the total wear and tear on the asset over its life and reduces the asset's book value on the balance sheet.