I am finding difficult understand following code in angular

let user = new User();
    user = {...this.frm.value};   // what this line does ??
    
    this.userService.post(user).then(respone => {
      console.log(respone);
    });

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- deleteUser(user: User): void {
    this.userService.deleteUser(user.id)
      .subscribe( data => {
        this.users = this.users.filter(u => u !== user);      // whats this line does??
      })
  };
 
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- onSubmit() {
    this.userService.updateUser(this.editForm.value)
      .pipe(first())    // whats this line does??
      .subscribe(
        data => {
          this.router.navigate(['list-user']);
        },
        error => {
          alert(error);
        });
  }