Being ethical means conforming to accepted moral standards. Applied to the work environment, it means that an ethical person has a higher standard than just avoiding a certain behavior or practice because it is illegal. What matters it that it might be the wrong thing to do morally. Ethics can be applied to all aspects of business, from accounting to customer service.
Being ethical in accounting means that you keep the business's financial information correct to the best of your ability, that you don't falsify records and you don't move funds around to make the company look more sound than it is. Keeping accurate financial records is crucial in any company, especially those that report the information to stockholders. Shuffling funds among accounts can make a company look healthier than it is by hiding problems; this can mislead investors. Or it can be done to make the company look weaker than it actually is in order to lower the tax burden. Some movement of funds between accounts is completely legal. But if it's done to give the appearance that the company is doing better or worse than it is, it is considered ethical.
Customer service is where a lot of ethical problems occur. Customer service employees, or those working in retail, are not always completely truthful with customers. This is not always illegal, but it is unethical. One example of this would be a bait-and-switch sale, where a company advertises an item is on sale but does not have that item in stock. The goal is to get the customer in the door and then sell him a more expensive product. Customers must be able to depend on the businesses they patronize. Companies that function without ethical practices risk losing their customers.
Quality control is used to make sure the product being produced is up to standards. An ethical company would not ship out a product that is not within the industry parameters of safety or quality. But some companies set different standards for the same product depending on whom it is being sold to. This is not illegal and is a normal business practice, but some consider it unethical. An example might be the different standards in tire valves that are sold to car companies and retail locations. The car companies have a higher standard for what they expect in the tire valves they buy. Retail locations often don't impose the same standards on the manufacturer. Having more than one standard for the same product opens the door for a company to be accused of being unethical because it applies different standards to different classes of customers.