DataTypes in Axapta

primitive datatypes:

Anytype:	A placeholder for any data type.
Booleans:	Can only contain the values false and true.
Dates :	Contains day, month, and year.
Enums:	An abbreviation for enumerated text—a set of literals.
GUIDs :	A globally unique identifier.
Integers :	A number without a decimal point. To declare an integer, use the keyword int.
Reals :	Numbers with a decimal point, also called decimals.
Strings:	A number of characters. To declare a string, use the keyword str.
TimeOfDay:	Contains hours, minutes, and seconds. To declare a time, use the system type timeOfDay.
utcdatetime:	Contains year, month, day, hour, minute and second

composite Datatypes:

Arrays	An array is a list of items with the same data type and the same name—only the index differs.
Containers	A container is a dynamic list of items containing primitive data types and/or some composite data types.
Classes as Data Types	A class is a type definition that describes both variables and methods for instances (objects) of the class.
Delegates as data types	A delegate collects methods that subscribe to the delegate. The delegate specifies the parameter signature that all its subscriber methods must share. When the delegate is called, the delegate calls each of its subscribers.
Tables as Data Types	All tables defined in the database can be handled as class defination

For more information:  http://msdn.microsoft.com/en-us/library/aa853792.aspx