CodeIgniter path constants definitions

Question

I have come across this page

https://www.codeigniter.com/user_guide/general/reserved_names.html

Could someone please explain to me what fo

Answer 1

You can find its short definition in index.php on the root of your CI folder.

EXT: The PHP file extension
FCPATH: Path to the front controller (this file) (root of CI)
SELF: The name of THIS file (index.php)
BASEPATH: Path to the system folder
APPPATH: The path to the "application" folder