[Lazarus] Rather lost in help - TOCNode?

[Reinier Olislagers]

Looking for where exactly CHM help gets the list of help
nodes/identifiers that currently causes context-sensitivive help for LCL
to pop up the help selector with 2 identical items.

components\chmhelp\packages\idehelp\chmlcl.pas contains:
procedure RegisterLclHelpDatabase;
var
  FPDocNode: THelpNode;
  DirItem: THelpDBISourceDirectory;
begin
  if Assigned(LCLHelpDatabase) then Exit;
  LCLHelpDatabase := TLclChmHelpDatabase(
    HelpDatabases.CreateHelpDatabase(sLclUnits, TLclChmHelpDatabase, True));

  // FPDoc nodes for units in the LCL
  FPDocNode := THelpNode.CreateURL(LCLHelpDatabase,
    'LCL - Lazarus Component Library Units',
    'file://index.html');
  LCLHelpDatabase.TOCNode := THelpNode.Create(LCLHelpDatabase, FPDocNode);
...

What is this TOCNode? Is this used to look up keywords to get a URL for
chm help to open?