please explain this program

include #define SIZE 10 int whatIsThis( const int bil, size_t p): // function prototype int fanct ovoia n begins progran execution int x; /I holds return value of function whatIsThis // initialize array a int a[ SIZE ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10); x = whatIsThis( a, SIZE ); printf( "Result is Xd ", x ); // end main /I what does this function do? int whatIsThis( const int b[l, size t p) // base case return bI e J; ) // end if else t // recursion step return b[ p 1 ]+ whatIsThis( b, p 1); // end else ) I/ end function whatIsThis