In Entity Relationship which type of relationship represents the association between entity types.

In Entity-Relationship (ER) modeling, the type of relationship that represents the association between entity types is generally referred to as a relationship set. This can involve different types of cardinalities, such as:

1. One-to-One (1:1): A single entity from one entity set is related to a single entity from another entity set.
2. One-to-Many (1:N): A single entity from one entity set can be related to one or more entities from another entity set, but those entities from the second entity set can only relate back to that one entity.
3. Many-to-One (N:1): Multiple entities from one set can be associated with a single entity from another set.
4. Many-to-Many (M:N): Entities from both sides can be associated with multiple entities from the other side.

These relationships help define how data is structured and interacted with in databases, making them crucial for effective data modeling. Understanding these relationships allows for efficient retrieval and manipulation of data within a relational database system.