Data type is a keyword in any languages. It says that in what way we are going to represent our data. If U want to use whole numbers then u can select Integer as ur data type, if u want to use letters u can use character or string data type. It is actually used to say in what format our data is going to be used in our program.
Data variable is the instance of the data type. It is used to store the value. But it can store the value according to the range defined in the data type. For example if u create a data variable for integer as
then c can store the values from -32768 to +32767