If you are an experienced Joomla user, this Joomla site might seem very familiar but maybe also very different.
The biggest change, since the very early versions of Joomla is the new administrator interface and the adoption of responsive design.
Hundreds, if not thousands of other enhancements have also been made.
How involved you choose to become in Joomla is entirely your choice.
A bit like driving a motor car - you do not have to know every part and how it works - you can be quite happy and content to 'just drive' - that's fine.
Alternatively - you can delve into significantly greater depth.
If you follow what is happening to Joomla, for example a major new release / version is being developed - you may choose to carry out tests - these tests can give you a very useful advanced "warning" of not only how the next major version Joomla will look and work, but how your existing extensions - components, templates, modules - will work alongside the up-and-coming Joomla release.
For example, here at UsingJoomla.com we were testing Joomla 2.5.0 (yes, way back then !) while Joomla 1.5.x (yes - that was even further back) was in use and being supported.
Now - in a test environment we are testing our extensions, components, plugins, templates, modules - on Joomla 4 - from when Joomla 4 was officially released - giving us a good "heads-up".