There are three broad ways to value a business: by what it earns, by what similar businesses have sold for, and by what it owns. Each answers a slightly different question.
Earnings
Most trading businesses are valued on their maintainable earnings. The question is what a normal year looks like, and what a buyer would pay for that stream of profit.
Assets
An entity that holds property or investments is usually valued on its net assets instead.
Comparable sales
Sales of similar businesses are used as a check on the result where good evidence exists.