Purchasing, or buying, is a certain kind of monetary exchange of user rights. Each purchase is an event in which an agent voluntarily pays to acquire something tangible or intangible, or for the performance of a service, which another agent sells in that event. Payment might be either in money or via the exchange of other assets. A buying event might include subevents of negotiating, paying, and the transferring of the purchased thing to the buyer. Examples of buying include: purchasing fighter jets for the Navy, buying a Pepsi from a vending machine, ordering dinner at a restaurant, acquiring a life insurance policy for oneself, mail-ordering clothes from Sears, and buying somethnig at a farmers’ market.
Shopping can be used to describe any events in which the performer pursues the purchase of something, whether or not there is an actual purchase. Shopping may involve looking for something, gathering information, assessing that information, and (optionally) buying.