There are a lot of Content Management Systems to mention, but only a few tastes good for a web developer, like me.
Content Management Systems help you manage your website such as adding, editing, or deleting/removing contents including media. It is very helpful, especially if you have a website that constantly updates, for example, a blog.
For me, the best CMS that I have used so far are the following:
Wordpress - this has been the CMS that I've been using for most of the websites that I made. I chose this because it has a lot of cool plugins and in terms of SEO, it is wise. For asking support, there are a lot of people in the web who can help you if you have troubles setting up your first Wordpress Website. There are also a lot of developers who are developing themes and plugins for this CMS.
Joomla - for creating web portals, I suggest this. It has a cool feature of managing registered accounts. If you also consider views, it has a lot of different views, though unlike Wordpress, assigning custom templates for pages is harder.
Drupal - if you love the thrills in developing websites, go for this. I, however, do not recommend this to starters because it is way too complicated to start with. For those who love building their own stuff, I suggest this.
