What does inptr and outptr mean

Question

Does anyone know what inptr and outptr mean? I know it's short for in and out pointer, but I just can't seem to grasp the purpose of it? Also if you can tell me why FILE is in there too id appropriate it.
Thank you!

char *infile = argv[1];
char *outfile = argv[2];

// open input file
FILE *inptr = fopen(infile, "r");
if (inptr == NULL)
{
printf("Could not open %s.\n", infile);
return 2;
}

// open output file
FILE *outptr = fopen(outfile, "w");
if (outptr == NULL)
{
fclose(inptr);
printf("Could not create %s.\n", outfile);
return 3;
}