what is primary key in ms access

A primary key is a field or set of fields with values that are unique throughout a table in MS Access. It is used to refer to entire records and allows you to create a unique identifier for each row in your table. Each table can only have one primary key. Access can automatically create a primary key field for you when you create a table, or you can specify the fields that you want to use as the primary key. To set a tables primary key, you can open the table in Design view, select the field or fields you want to use as the primary key, and then click Primary Key on the ribbon. Access automatically creates an index for the primary key, which helps speed up queries and other operations. Access also ensures that every record has a value in the primary key field, and that it is always unique. A primary key is important when creating a database in Access because it provides a means to specifically and uniquely identify a row of data (or record) in a table.