whats the point of #defines in c+= code example

Example 1: #define in c

#include 

#define NAME "TechOnTheNet.com"
#define AGE 10

int main()
{
   printf("%s is over %d years old.\n", NAME, AGE);
   return 0;
}

Example 2: c define

#define SIZE 42
#define MSG "Hello, World!"