An owner can sell the company’s assets outright, or he can sell his stock in the company (or units if it is a limited-liability company). Stock sales tend to benefit the seller, while asset sales are more beneficial to the buyer.
Asset buyers are getting the company’s physical equipment, facilities and customers, as well as intangibles such as trademarks and goodwill, and as a result are generally protected against prior claims against the business. For example, the previous owners would most likely be responsible if an environmental claim were made against their former property or if an employee hired on their watch filed some sort of lawsuit.
Stock purchasers, in contrast, are buying the company itself and thus are exposed to all of its potential problems. This is why most sales of small, closely-held businesses are structured as asset sales.
Selling the business to its managers is also a popular option. An owner might go this route when the company has a trusted, entrepreneurial management team that wants to carry on the business.