Fields in Salesforce are similar in concept to a database column; they store the data for the object records. An object record is analogous to a row in a database table.
Standard fields are predefined fields that are included as standard within the Salesforce CRM application. Standard fields cannot be deleted but nonrequired standard fields can be removed from page layouts, whenever necessary.
With standard fields, you can customize visual elements that are associated with the field, such as field labels and field-level help as well as certain data definitions such as picklist values, the formatting of auto-number fields (used as unique identifiers for the records), and the setting of field history tracking. Some aspects, however—such as the field name—cannot be customized and some standard fields (such as Opportunity Probability) do not allow the changing of the field label.