A structure is the basic building block of data structures, it contains a collection of different "fields", possibly with different data types which are typically fixed in number and sequence.

Example

struct Date {
	int year;
	char month[30];
}

int main() {
	struct Date d1 = {2000, "January"};
	struct Date d2 = {2001, "September"};

	printf("%s %d", d1.year, d1.month); // January 2000
	printf("%s %d", d2.year, d2.month); // Septeber 2001
	
	d1.month = "October";
	
	printf("%s %d", d2.year, d2.month); // October 2001
}