Durability and tangibility.
Nondurable goods are tangible goods (such as shampoo) normally consumed in one or a few uses. Because these are purchased frequently, the appropriate strategy is to make them available in many locations, charge a small markup, and advertise to induce trial and build preference.
Durable goods are tangible goods (such as refrigerators) that survive many uses, require more personal selling and service, command a higher margin, and require more seller guarantees.
Services are intangible, inseparable, variable, and perishable products (such as haircuts) that normally require more quality control, supplier credibility, and adaptability.