Final answer:
Deferred or unearned revenue is money received by a company for products or services that have not yet been delivered; it is classified as a liability in accounting.
Step-by-step explanation:
Deferred revenue, also known as unearned revenue, is money received by a company for goods or services that have not yet been delivered or performed. In accounting terms, this is considered a liability because it represents an obligation to the customer. It is not yet ‘earned’ by the company, and therefore, it does not become part of the equity or revenue until the company fulfills its part of the transaction, usually by delivering a product or service. In the classification of accounts, deferred revenue would be classified as an 'L' for liability.