Who knows about CMS (Content Management Solution) ؟

Hi, I would like to ask, who knows about CMS, what is it, how is it done and why is it used??
CMS as you said is an Content management System for websites webmasters uses it to control their own website easly and smoothly by logging into a control panel using username and password and webdesign and development companies uses it to make easly edited websites to clients to control and edit easly by clients