The Available Operators window includes a list of operators that can be used when creating an expression.

Filter The Filter option determines which operators are shown in the list of operators.
List The list of operators shown depends on the Filter specified.

Note: Operators are used to modify a value, or compare two values. Modifying operators are mathematical (addition, subtraction, multiplication, division, exponential, equals, etc.), while comparison operators are not (equal to, less than, greater than, etc.). Modifying operators can be used as part of a Function, while comparison operators are generally used for filtering purposes.
 
For example, the expression DATE$(DATENUM( ) + 7) uses two Functions, DATE$( ) and DATENUM( ), and the addition operator. The result of this expression is a string representation of the date seven days after the current system date.

The Insert button will close the window and insert the highlighted operator into the expression being defined. Double-clicking an operator in the list does the same thing.

The Cancel button will close the window without changing the expression being defined.