Please explain why the output is like this

fp = fopen("a.txt", "a+");
if (fp == NULL)
{
    printf("Failed to create file".\n");
    return 1;
}
while (1)
{
    printf ("Fruit name: ");
    scanf("%s", str);
    if(strcmp(str,"end")==0)
    {
        break;
    }
    else if (strcmp(str, "list") == 0)
    {
        fseek(fp, 0, SEEK_SET);
        while (1)
        {
            fgets(str, sizeof(str), fp);
            if (feof(fp))break;
            printf("%s", str);
        }
    }
    else
    {
        fprintf(fp, "%s\n", str);
    }

}
fclose(fp);

return 0;