What is difference between foreign key and reference key?

Question

I am very confused about those two terms. Are they the same or different?

Some books and people say they are the same and others say they are different.

I tr

Answer 1

There are 2 ways to declare a foreign key(s):

1. if the foreign key is a SINGLE attribute:
   REFERENCES ()

2. if foreign keys are a LIST of attributes

FOREIGN KEY () REFERENCES