A one-to-many relationship, often referred to as a "master-details" or "parent-child" relationship, is the most usual relationship between two tables in a database.
Common scenarios include customer/purchase data, patient/medical-record data, and student/course-result data. For example, each customer is associated with at least one order record. Valued customers have many order records involving significant sums and often a user needs to view one in connection with the other. In a one-to-many relationship, a record in Table A can have (none or one or) more than one matching record in Table B, but for every record in Table B there is exactly one record in Table A.
For example, say you have Orders table and Order Details table , where order number is a common field in each. You can create a master-details relationship that will enable you to navigate through the Orders and jump to Order Details that belong to current order only.