Foreign Key

Hello Sue

Thank you for your question and welcome to the forum.

A foreign key is used to be able to link two tables with each other - typically what is used as a foreign key in one table will be the primary key in another; then the tables are linked with each other by these keys (primary+foreign).

There is a good explanation with an example database available via the link below:
http://www.databasedev.co.uk/primary_foreign_key_constraints.html

Kind regards
Amanda