An Association is used to associate information and Artifacts with Flow Objects. Text and graphical non-Flow Objects can be associated with the Flow Objects and Flow. An Association is also used to show the Activity used for compensation.
— BPMN 2.0.2 Standard, 8.4.1, Association
Provides a way to connect a Data Objects to any other element in a BPMN diagram. They do not have any impact on the execution of the business process.