Content Management Systems (CMS) are one of the most important elements of the internet. It makes web development, web design and maintenance very easy. Nowadays two CMSs that became popular are:
Although WordPress is a blog posting script, with the help of a few plug-ins and customization it can be used as a very good CMS.
Joomla is a very good and popular CMS, but I think it has some problems with security. I created Joomla site more than 3 times, but it got hacked every time. In this case I think WordPress is much better, but it all it depends on who is using it.
I think both of them have their own specialties. Utilizing their specialties can help one in understanding their main features.
Joomla is more powerful and has more preinstalled features than WP. But WP is easier to use. Another thing is that almost all the themes and plug-ins of WP are free, although there are also a lot of buyable plug-ins available. In this case I thing WP is better than Joomla. But with Joomla you can make more professional websites.