Simple merge is a pattern in which two or more distinct branches are merged without synchronization. Each enablement of an incoming sequence results in enabling of the subsequent activities. If there is more than one enablement, the subsequent activity will be executed more than once. In BPMN, this pattern is supported by a converging XOR gateway.
In the grocery shopping example above, every member of the family bringing in items to the checkout counter will result in the cashier scanning the items as they arrive. Mom buying milk, Dad getting groceries and kids getting candies may happen in any order but each time one of the these items arrive, the cashier will scan the items. There would be a problem if there are other customers besides this family waiting in the line for sure!