Basically, in numbers data_type like integer we have some range of 'int' in both side of 0, i.e., negative as well as positive.
we store negative as well as positive value in integer type variable.
In signed data_type we also have capability to store negative values.
-By default when we declared any data_type then it is signed
In unsigned variable data_type we only store positive values(including 0).
-Or when we want to store only positive value in that case we use unsigned integer.
unsigned int age;
-Because age can't be negative.
unsigned data_type variable_name;