At its most basic level, profit is defined as the difference between a business' income and its costs. When you evaluate whether a specific project was profitable, you typically look at gross profit. This is the project's revenue minus all of the direct costs related to it, such as personnel costs or any equipment that was required.
However, there are other items that fall into the cost or expense category, which should be included to get a clearer picture of your profitability.
These fixed or indirect costs are the costs associated with doing business and are also known as overhead. They might include rent, utilities, phone, equipment, interest on bank loans, taxes, employee salaries that are not billed to a specific project and staff training.
To determine profit, you must subtract all of your fixed or indirect cost from gross profit.

Cash flow refers to both the revenue and expenses that flow into and out of a company's cash account. Cash may flow into your business through sales or operations, financing or investing. It may flow out to pay expenses or make investments.

Cash flow is crucial to a business' survival. To be successful, companies must have sufficeient cash on hand to pay employees, vendors and others in a timely manner. They should also have adequate cash available to put back into the business.

To manage your cash flow, you must shorten the length of time it takes to turn your services or product into receivables into cash, while delaying outlays of cash as much as possible.

Overhead refers to any business expenses that are necessary for running the business, but do not directly generate revenue. Overhead may include expenses for accounting, advertising, depreciation, insurance, interest, legal fees, labor not directly related to generating income (such as clerical support), rent, supplies, taxes, telephone and utilites.