1. In object-oriented programming, association defines a relationship between classes of objects that allows one object instance to cause another to perform an action on its behalf. This relationship is structural, because it specifies that objects of one kind are connected to objects of another and does not represent behaviour.
2. An association determines how many tuples (records) of a table can be mapped to tuples (records) in another table.
This element is used in a entity block diagram to describe the interactions and dependencies between two entities and their relationships to each other.
https://en.wikipedia.org/wiki/Association_(object-oriented_programming) (1.); http://www.datenbanken-verstehen.de/lexikon/assoziation/ (2.)