Tables hold data about employees and the projects to which they are assigned. Each project can involve more than one employee and each employee is able to be occupied on more than one project

Each record in Table A relates to one, and only one, record in Table B, and each record in Table B relates to one, and only one, record in Table A.

Record in Table A can relate to zero, one, or many records in Table B. Many records in Table B can relate to one record in Table A.