Control panels are how you access and manage different tools that your hosting account has in it. You can access your server files, set up ftp accounts, databases and manage domains. Depending on the type of control panel you have you will have access to a number of different features. There are 3 main types of control panels.
cPanel is the most commonly used and easy to navigate control panels. Most developers and website designers are used to the layout and the features that it offers.
Is a little lest popular but is preferred by some developers and hosts.
Custom control panels are usually offered by hosting companies that specialize in one area of expertise. Also, major brands like to create their own control panel for more personalization.
There are hundreds of different installs possible on servers. With from within the control panel there will either be a one-click installer or some way to manage databases and files. Depending on the type of website you are probably looking for one of these types of installs: Joomla, WordPress or Drupal. There lots of other content management systems out there, but these are the most commonly used.