From Wikipedia

Shoplifting

Shoplifting
(also known as five-finger discount,
or shrinkage within the retail industry) is theft of goods from a retail establishment. It is one of the most common property crimes dealt with by police and courts.

Most shoplifters are amateurs; however, there are people and groups who make their living from shoplifting, and they tend to be more skilled. Generally, criminal theft involves taking possession of property illegally. In the case of shoplifting, though, customers are allowed by the property owner to take physical possession of the property (holding it in their hands or in a shopping cart controlled by them, for instance). This leaves areas of ambiguity that could criminalize some people for simple mistakes (such as accidental hiding of a small item or forgetting to pay). That is one of the reasons that penalties for shoplifting are generally lower than those for general theft.However, in practice most stores are aware of the hazards of making a false arrest and are instructed to be sure there is no doubt (ambiguity) before they make the arrest. Trained staff know the basics, observe the person, observe the item, observe the concealment (theft), keep constant unrestricted contact with the shoplifter, wait until the shoplifter leaves the store - make the arrest. As for penalties being less for shoplifter vs for "general" theft, in most states there is no specific "shoplifting" law; rather, shoplifting is charged as simply as "theft." If the dollar amount of the item stolen is low it is a lower (less serious) theft crime. It the dollar value is higher, it is a more serious theft crime.