Any combination of operators, constants, literal values, functions, and names of fields (columns), controls, and properties that evaluates to a single value. You can use expressions as settings for many properties and action arguments; to define calculated controls in forms, reports, and data access pages; to set criteria (search conditions) or define calculated fields in queries; and to set conditions in macros. In a Microsoft Access project, you can use expressions to define check constraints.
You also use expressions in Microsoft Visual Basic.