Variables are names that are bound to data values (in the case of primitive types) or the location of data values (in the case of reference types). Variables are declared by specifying a data type, a name, and optionally, an initial value. With the exception of the string data type, once declared, new values can be computed and assigned to variables as needed. Strings are immutable and variable assignment causes a new string value to be created and bound to the string variable.