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Two words show up everywhere in accounting: revenue and expenses. They’re the money a business earns and the money it spends. Get these two straight and the Income Statement — the report that says whether you made a profit — suddenly reads like a simple subtraction.

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Revenue — the money you earn

Revenue is the money a business earns from doing what it does: selling a product, providing a service, charging for a subscription. It’s the top line — the reason the business exists in the first place. Picture a bakery. Every loaf it sells brings in revenue. Add up a day’s sales and that total is the day’s revenue. It’s the inflow that everything else gets measured against. One thing to hold onto: revenue is about what you earned, not necessarily the cash sitting in your account today. That subtlety has its own page — accrual vs. cash — but for now, just think of revenue as money earned from the work.

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Expenses — the money you spend to earn it

An expense is money the business spends to keep running and to earn that revenue: rent, salaries, electricity, flour for the bakery. If revenue is what comes in, expenses are what goes out to make it happen. Expenses aren’t a bad thing — they’re the fuel. You can’t sell bread without buying flour and paying the baker. The point of accounting isn’t to avoid expenses; it’s to know exactly what they are so you can tell whether the revenue was worth it.

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Cost — close to expense, but not identical

People use cost and expense as if they mean the same thing, and in casual talk they nearly do. The small distinction worth knowing:
  • A cost is what you pay to get something — the price of acquiring a resource. Buying an oven for the bakery has a cost.
  • An expense is a cost counted against the revenue of a period — the portion that’s “used up” in earning this stretch’s income. The flour baked into today’s bread is an expense today.
In short: a cost becomes an expense once it’s used up in the work of earning revenue. The oven is a cost when you buy it; the slice of its wear-and-tear that helped make this month’s bread becomes an expense this month. Don’t over-think the cost-versus-expense line — just know that “cost” leans toward acquiring, and “expense” leans toward using up to earn revenue. Follow one bag of flour through the bakery and the whole chain falls into place:

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Why they matter to the Income Statement

These two words are the entire engine of the Income Statement:
  • Start with revenue — the money earned.
  • Subtract expenses — the money spent earning it.
  • What’s left is profit (or, if expenses were bigger, a loss).
A month at the bakery, in one line: $1,000⏟revenue−$700⏟expenses=$300⏟profit\underbrace{\$1{,}000}_{revenue} - \underbrace{\$700}_{expenses} = \underbrace{\$300}_{profit} That’s it. Revenue minus expenses tells you whether the business actually made money over a period. Every other line on the statement is just a more detailed way of grouping those two ideas. And that profit doesn’t just disappear — it flows into equity. Earn a profit and the owners’ stake in the business grows; run a loss and it shrinks. That’s the quiet link back to Assets, liabilities & equity: the Income Statement is the story of how equity changed over a period.

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In short

  • Revenue is the money a business earns from its work; expenses are the money it spends to earn that revenue.
  • A cost is what you pay to acquire something; it becomes an expense once it’s used up in earning a period’s revenue.
  • The Income Statement is simply revenue minus expenses — the difference is your profit or loss.
Next upNow you know the five account families. Next, see how every change to them gets written down — as Debits and credits.