launch.joomla.org is a great tool to learn and explore Joomla!
Joomla is a Content Management System (CMS); a software to manage a website. Joomla is an open source software and is totally free to download and use, go to the Joomla website. Also many extensions and templates are free, but also paid versions of exist. Beside the server, domain etc to host the site, it is possible to build a good, modern and advanced web site without any cost, ads or other hidden drawback.
I have been using Joomla for a couple of years. For example I use Joomla for this website, hemrin.com.
You can try out Joomla for free, without bothering of any installation etc via launch.joomla.org. It only take a few minutes to register! The biggest problem might be to decide upon name for this website. If you want to, you can go on with it as a real website. If you are curious to have your own web site, for personal or business reasons, or the company you work for, I suggest give Joomla a try via launch.joomla.org.
But also for us who have the Joomla based websites release, this free trial is a great tool. I use launch.joomla.org for test and development purposes. For example new extensions I am interested in. Only reading about an extension does not always give a clear view. Instead of installing it on my real web site directly, I can use my playground at launch.joomla.org to do those trials. Great and recommended for all Joomla users!