A null terminated string of 8 bits characters (i.e. a C string.) You have to scan the string in order to skip it to the next element.
Flash also makes use of Pascal Strings. Those strings start with a size. In all instance, the size of the string is defined on one byte (char). In this case, we declare the string with a construct as follow:
char f_string_size; char f_pascal_string[f_string_size];