CMS Portal

[jeeva]

hi,

i have configured Joomla and Drupal CMS portal into my local server.Its working fine.
now i want to know this CMS portal...I am new in this.
According to my knowledge we can manage the content of a site  by using this.. am i right?
instead of that we can configure one editor(like Spaw,FCK) into our site and we can manage the content.
why shoud we use this portal? Any advantage is there?

still it is difficult to understand. will u please tell me
wt is CMS portal?
wt we can do in that?
wt's the benefit we will have? and
how to use this effectively?

sorry for lack of knowledge.......

...jeeva