Purpose of Chg control system

 Can somebody explain purpose of change control system and/or diff of chg control system with ICC?

In my understanding chg ctrl system is used for documentation purpose (version control) for change processed through ICC. and it comes under confg control sytem.

I am confused between ICC and change control system..

can someone explain please?

 

 p 93 4.5

ICC is a process

p94 para4 

describes 

config mgmt system 

config control and change control

also glossary definitions