What kind of type are these classes?

[eluser]Unknown[/eluser]
Hi!

I'm new to CI and started therefor a simple project.
In my project I'm trying to parse a directory to my class structure.
something like that:

Code:

...

$folder = new Folder();
foreach($files as $file)
{
  if(is_dir($file)) {
    $folder->add(new Folder($file));
  }
  else if (is_file($file)) {
    $folder->add(new File($file));
  }
  ...
}
...

I guess i dont understand what kind of Class (eg library, helper, models(only for db?)) is what for.
What kind of classes are Folder and File?
Are they Helper, Library,..?