ArcObjects Library Reference (Editor)

IEditor Interface

Available with ArcGIS Desktop.

The IEditor interface is the main interface used to control the actions of the editor. For example, use the members in this interface to start and stop an edit session, create and manage edit operations, and set the editor's current task.

[C#]

private IEditor m_editor;
private IApplication m_application;
// Would get the app by using hook during implementation of CreateCommand
      ...
      UID uID=new UID();
      uID.Value="esriEditor.Editor";
      if (app == null)
        return;
      
      m_editor=app.FindExtensionByCLSID(uID) as IEditor;
//To use the Editor name instead of UID
     ....
       if (app == null)
        return;
       m_editor=app.FindExtensionByName("ESRI Object Editor") as IEditor;

[Visual Basic .NET]

In VB.Net you would get the reference to IApplication from hook in the ICommand::OnCreate() hook parameter
Private m_editor As IEditor
Private m_application As IApplication
...
Public Overrides Sub OnCreate(ByVal hook As Object)
    If Not (hook Is Nothing) Then
      If TypeOf (hook) Is IApplication Then
        m_application=CType(hook, IApplication)
      End If
    Else
      Exit Sub
    End If
    Dim uID As New UID
    m_application=hook
    uID.Value="esriEditor.Editor"
    m_editor=m_application.FindExtensionByCLSID(uID)
  End Sub
Or it can be found by name. 
...
  ...
  m_editor=m_application.FindExtensionByName("ESRI Object Editor")
End Sub