Which type of keys links to multiple rows in another entity?

The correct choice is foreign keys. Foreign keys are used in relational databases to establish relationships between tables. They are a fundamental concept for maintaining referential integrity within the database. When a foreign key from one table points to the primary key of another table, it allows multiple rows in the first table to be linked to a single row in the second table. This means that one record can have multiple related records, creating a one-to-many relationship.

In typical usage, if you have a 'Customer' table with a unique identifier as the primary key, a 'Orders' table might include a foreign key that references the 'Customer' table. This way, multiple orders can be associated with a single customer, highlighting how foreign keys facilitate such relationships.

The other types of keys mentioned do not serve this specific function. Type keys and array keys are not standard terms used in the same context as foreign keys in relational database design, while unique keys refer to constraints that ensure the uniqueness of values in a column but do not facilitate multi-row relationships in the way foreign keys do.