Explenation about some declared variables.

Dear experts,

I have found an example on EE how to load and save treeview to and from a database.
I tried to understand the code so i have a couple of questions about the declared variables.
I have put a part of the code in the Code-section.
Who can explain it to me what the following variables are for:
=> fStatus: byte
=> fSaveImmediate: boolean;
 => fIsNew: Boolean;
=> fSaver: TAdoQuery;

type
  TItem = class(TObject)
  private
    fStatus: byte;
    fParentID: integer;
    fNodeText: string;
    fID: integer;
    fData: string;
    fSaver: TAdoQuery;
    fChanged: Boolean;
    fSaveImmediate: boolean;
    fIsNew: Boolean;
    fImageIndex: integer;
    procedure SetData(const Value: string);
    procedure SetNodeText(const Value: string);
    procedure SetParentID(const Value: integer);
    procedure SetStatus(const Value: byte);
    procedure SetImageIndex(const Value: integer);
  protected
    procedure Changed; dynamic;
  public
    constructor Create(aSaver: TAdoQuery; AId, AParentID: integer; AStatus: byte);
    constructor LoadFromDataset(aSaver: TAdoQuery);
    procedure Save;
    procedure Delete;
    procedure BeginUpdate;
    procedure EndUpdate;
  published
    property ID: integer read fID write fID;
    property ParentID: integer read fParentID write SetParentID;
    property ImageIndex: integer read fImageIndex write SetImageIndex;
    property Status: byte read FStatus write SetStatus;
    property Data: string read fData write SetData;
    property NodeText: string read fNodeText write SetNodeText;
  end;
 
 
 
{ TItem }
 
procedure TItem.BeginUpdate;
begin
  fSaveImmediate := false;
end;
 
procedure TItem.Changed;
begin
  fChanged := True;
  if fSaveImmediate then Save;
end;
 
constructor TItem.Create(aSaver: TAdoQuery; AId, AParentID: integer;
  AStatus: byte);
begin
  inherited Create;
  fChanged := False;
  fSaveImmediate := True;
  fIsNew := True;
  fSaver := aSaver;
  fID := AID;
  fParentID := AParentID;
  fStatus := AStatus;
  fNodeText := '';
  fData := '';
end;
 
procedure TItem.Delete;
begin
  //
end;
 
procedure TItem.EndUpdate;
begin
  fSaveImmediate := True;
  if fChanged then
    Save;
end;
 
constructor TItem.LoadFromDataset(aSaver: TAdoQuery);
begin
  Create(aSaver, 0, 0, 0);
  if not aSaver.IsEmpty then
  begin
    fId := aSaver.FieldByName('ID').AsInteger;
    fParentID := aSaver.FieldByName('PARENT').AsInteger;
    fStatus := aSaver.FieldByName('STATUS').AsInteger;
    fNodeText := aSaver.FieldByName('NAME').AsString;
    if aSaver.FindField('DATA') <> nil then
      fData := aSaver.FieldByName('DATA').AsString;
    fImageIndex := aSaver.FieldByName('IMAGE_INDEX').AsInteger;
    fIsNew := False;
  end;
end;
 
procedure TItem.Save;
begin
  if fIsNew then
    fSaver.SQL.Text :=
      'insert into tree (parent, name, status, image_index, data) values (:v1, :v2, :v3, :v4, :v5)'
  else
    fSaver.SQL.Text :=
      'update tree set parent = :v1, name = :v2, status = :v3, image_index = :v4, data = :v5 where id = :v6';
  fSaver.Parameters.ParamByName('v1').Value := fparentID;
  fSaver.Parameters.ParamByName('v2').Value := fNodeText;
  fSaver.Parameters.ParamByName('v3').Value := fStatus;
  fSaver.Parameters.ParamByName('v4').Value := fImageIndex;
  fSaver.Parameters.ParamByName('v5').Value := fData;
  if not fIsNew then
    fSaver.Parameters.ParamByName('v6').Value := fId;
  fSaver.ExecSQL;
  if fIsNew then
  begin
    fSaver.SQL.Text :=
      'SELECT id from tree order by id desc';
    fSaver.Open;
    fId := fSaver.FieldByName('ID').asInteger;
    fSaver.Close;
    fIsNew := False;
  end;
  fChanged := False;
end;
 
procedure TItem.SetData(const Value: string);
begin
  if fData <> Value then
  begin
    fData := Value;
    Changed;
  end;
end;
 
procedure TItem.SetImageIndex(const Value: integer);
begin
  if fImageIndex <> Value then
  begin
    fImageIndex := Value;
    Changed;
  end;
end;
 
procedure TItem.SetNodeText(const Value: string);
begin
  if fNodeText <> Value then
  begin
    fNodeText := Value;
    Changed;
  end;
end;
 
procedure TItem.SetParentID(const Value: integer);
begin
  if fParentId <> Value then
  begin
    fParentID := Value;
    Changed;
  end;
end;
 
 
procedure TItem.SetStatus(const Value: byte);
begin
  if fStatus <> Value then
  begin
    FStatus := Value;
    Changed;
  end;
end;
 
end.

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