Q:

What is the applescript code to open a folder

Right now I am using this code:
    open folder

and it seems like it can not find the folder.
Do I have to specify a folder?

A:

Basically open does not open folders.
You have to open a folder via the Finder and specify an HFS string path, alias or Finder folder specifier:
tell application "Finder" to open (path to desktop)

or
tell application "Finder" to open home

or
tell application "Finder" to open folder "Applications" of startup disk

