What is the 'key field' called that is used in a relationship between tables value match with the primary key in another table?

User login

5 + 3 =
Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.

What is the 'key field' called that is used in a relationship between tables value match with the primary key in another table?

Secondary key

Foreign Key

Candidate key

Alternate key