fgets와 gets의 차이점??

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
 
typedef struct data
{
        char name[20];
        char number[20];
        struct data *next;
}phone;
phone *head, *tail;
void init(void)
{
        head=(phone*)malloc(sizeof(phone));
        tail=(phone*)malloc(sizeof(phone));
        head->next=tail;
        tail->next=tail;
}
void insert()
{
        phone *t;
        t=(phone*)malloc(sizeof(phone));
 
        printf("Input name: ");
        scanf("%s",t->name);
  fflush(stdin);
        printf("Input Tel Number: ");
  scanf("%s",t->number);
  fflush(stdin);
        printf("-------> Data Inserted\n");
 
        t->next=head->next;
        head->next=t;
}
int remove(char *s)
{
 phone *t,*p;
 p=head;
 t=p->next;
 while(strcmp(s,t->name) !=0 && t!= tail)
 {
  p=p->next;
  t=p->next;
 }
 if(t==tail)
  return 0;
 p->next=t->next;
 free(t);
 return 1;
}
void print()
{
 phone *p;
 p=head->next;
 while(p!=tail)
 {
  printf("%s\t%s\n", p->name,p->number);
  p=p->next;
 }
}
 
 
 
int main(int argc,char *argv[])
{
 init();
        int a;
  char buf[20];
        while(1)
        {
                printf("-----Menu-----\n");
                printf("  1. Insert\n");
                printf("  2. Remove\n");
                printf("  3. Search\n");
                printf("  4. Print All\n");
                printf("  5. Exit\n");
                printf("Choose the item: ");
                scanf("%d",&a);
                getchar();
 
                switch(a)
                {
                        case 1: 
                                 insert();
                                 break;
                        case 2: 
                                  printf("삭제할 이름: ");
                                  <span>fgets(buf,20,stdin); //gets(buf)로 고치면 밑의 remove함수가 제대로 실행됨</span>
                                  remove(buf);
                                  break;
                        case 4: 
                                  print();
                                  break;
                }
  }
return 0;
}