Fgets and sscanf

This code should get the integers from the file, which is finput and sort it, and get the first integer in the file, which is the number of integers to be sorted, and the integers that follow are the integers that need to be sorted. I do not understand how fgets and sscanf work together. Can someone explain how fgets and sscanf work in this code?

FILE *finput;
int *array_int, c1, no_elem;
char numlines[500];

fgets(numlines, 500, finput); 
array_int = (int *)malloc(sizeof(int)*no_elem);
if ((sscanf(numlines, "%d", &no_elem) == 1) &&  array_int!= NULL)
{
    for(c1=0; fgets(numlines, 500, finput) != NULL; )  
    {
        if (sscanf(numlines, "%d", &array_int[c1])==1) 
        {
            ++c1;
        }
    }
}