Help needed with backtracking

Code:

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#include <stdio.h>

/* Entry FREE means the position is free to be traversed.
 * Entry WALL means the position can never be traversed.
 * Entry USED means the position has already been visited,
 * and should not be visited again to avoid running in circles.
 * Such entries USED are introduced during the search.
 */

#define FREE 0
#define WALL 1
#define USED 2

/* Our maze. */

#define ROWS 5
#define COLS 7

int maze[ROWS][COLS] =
        { { FREE, WALL, FREE, FREE, FREE, WALL, FREE },
          { FREE, FREE, FREE, WALL, FREE, WALL, FREE },
          { FREE, FREE, WALL, WALL, FREE, FREE, FREE },
          { WALL, FREE, FREE, FREE, WALL, FREE, WALL },
          { FREE, FREE, WALL, FREE, FREE, FREE, FREE } };

/* Initial length of shortest path, which is more than largest
 * possible length if any path exists. This value indicates no path exists.
 */

#define NOPATH (ROWS*COLS)

/* Length of shortest path. Initialized to upper bound, which would
 * indicate no path exists.
 */

int shortest = NOPATH;

/* Positions of mouse and cheese. */

#define MOUSE_ROW 2
#define MOUSE_COL 1

#define CHEESE_ROW 0
#define CHEESE_COL 6

/* First check if current position exists, and can be traversed (it is FREE),
 * and whether current path length is shorter than shortest path.
 * If cheese found, record length of path.
 * Otherwise, mark current position as used, and try moving up, down, left, right
 * by recursive calls, and then make position unused again.
 */

void find_cheese(int row, int col, int length)
{
  Complete function
}

int main()
{
    find_cheese(MOUSE_ROW, MOUSE_COL, 0);
    if (shortest < NOPATH)
        printf("Shortest path has length: %d\n", shortest);
    else
        printf("No path exists\n");
    return 0;
}

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This is a homework assignment. I have done a search on this forum regarding backtracking and I didn't find anything. What I need to do seems quite simple, completing the code by creating the function, because it's backtracking it has to be a recursive function. However, despite the guidance of the comments, I don't get it. What is meant by "current position"? Íf someone could explain that to me, I can finish the code myself. Thanks

Code:

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void find_cheese(int row, int col, int length)
{
  Complete function
}

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There are two bits of code which go in here

Code:

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if ( row == CHEESE_ROW && col == CHEESE_COL ) {
  if ( length < shortest ) shortest = length;
  return;
}

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This compares your position with the objective and returns

Now do this for all possible directions

Code:

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if ( maze[row+1][col] == FREE ) find_cheese(row+1,col,length+1);

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Don't forget to
- check the bounds of maze[row][col]
- mark the current position as used before making recursive calls.