Data Types distinguish certain types of data from others, this way a programming language can be more useful to authors. Variables created can hold any data type, and they are processed according to the data type we define. Every good programming language distinguishes data types when scripts run.

Here is a breakdown of the ActionScript 3.0 Data Types:

Data Type	Description
Boolean	Can hold only two possible values, true or false. If the value is not initialized it defaults to false.
int	Use for numbers. If you do not require a floating point number(decimal), use the int type for working with numbers in youe application. The default value for variables that are of the data type int is 0.
Null	Used to signify that a pointer intentionally does not point to (or refer to) an object. The Null data type contains only one value, null.
Number	Used for integers, unsigned integers, and floating-point numbers. To store a floating-point number, include a decimal point in the number. If your number has no decimal point, the number will be seen as an integer.
String	Represents a sequence of alphanumeric characters and symbols. For instance, "abc" is a string, as well as "abc123". This email address is also a string "bean33@somebeansite.com".
uint	Use the uint data type for special circumstances that call for non-negative integers. Has a value range from 0 to 4,294,967,295. The uint data type has an internal sign bit that is most appropriate for handling color values. For integer values larger than the maximum uint value, use the Number data type.
void	Contains only one value, undefined.
Object	The base class for all class definitions in ActionScript. The ActionScript 3.0 version of the Object data type differs from that of previous versions in three ways. Default value for instances of the Object class is null.