See attach file.
Array is used to define a group of data of same characteristics (but different values). For Example if one has to declare the number of students in a class, their ID numbers will be unique and different, but all will be +ve integers.
So if there are 100 students, instead of assigning a seperate variable to the ID number (like id1, id2, id3 ... so on) of each student it is defined ...
Array types are defined.