Hello, and welcome to the forum.
I believe you are asking about Cleaner\Advanced\Custom Files and Folders.
These are custom files to delete and folders to empty that are selected in Options\Include.
This is an advanced option that can have very negative effects on a computer if important system files are selected.
I advise that you ask for help when using any of the advanced options.
Heres a link to CCleaner Beginner's Guide.
http://www.internetrotsyourbrain.com/ccleanerbeginnersguide/Reading the guide will help you understand the functions of CCleaner so your questions here are better answered.
Jamin4u