Interaction refers to the way in which different components or objects within a system interact or communicate with each other to perform specific tasks or functions. Interaction can involve various types of communication, such as messages, events, or function calls.
For example, in a system where a customer places an order for a product, the interaction might be illustrated through a line connecting the customer object to the order object, and another line connecting the order object to the product object. The lines would represent the interactions between the objects, since the customer interacts with the order, and the order interacts with the product.