A CMS system is a Content Management System and is used to manage content on your website
let's say you are trying to build a website in HTML and CSS,
And you're like, maybe I should edit the header or the footer,
And so you open your index.html file, And you change that word in the header.
you do that same thing with page1.html, page2.html and contect.html.
that sounds like a pain in the ass, And that is where a CMS system comes into place.
The quick answer to this is NO!!
but if you want to learn to program YES you should definitely build a CMS system.
If you want to build a CMS system. you'll need a couple of programming languages like PHP and HTML.
there are lots of tutorials online available that will show you how to build a CMS system,
If you want to build a professional website, then you'll be better off using something like Wordpress or Joomla, Rather than building your own.
I recommend you to download Wordpress since this is the most popular tool available. since it is the most popular one,
If you want to build a website you probably want something like a CMS system, To manage your content.
remember that you shouldn't build your own CMS system, but download Wordpress or Joomla