In a database, such as Microsoft SQL Server, data is stored and organized in tables. Tables consist of a set of columns and a set of rows. The columns (also referred to as "fields") define what information you are storing about your object (such as name , description, color , and so on). The columns define how your data will look. This is referred to as the database schema. The rows (also referred to as "records") are your data ”each row represents a group of columns of information.
A primary key is a column in your table that guarantees row-level accessibility. This sounds more complicated than it really is. Think of the data in a table organized like a spreadsheet. To access a particular row, the data provider needs to be able to distinguish that row from the rest in an efficient manner. The primary key is any field (or set of fields) that can be used to guarantee uniqueness. For instance, common examples of a primary key include:
Identity field ”A special automatically incremented number field that stamps each record added to the table with a unique number. No two records in the table will have the same value in the identity field.
Social Security number ”A field like this will work just fine so long as each person is listed only once in the table.