Wordpress , Drupal and Joomla all are free and open source software and all three of them are written primarily in PHP and all supoorted MySQL as their database management system.
While there are a lot of similarities, but they are different in many aspects.They have different policies about what to include in the core software, how to handle modules and templates, how to deal with security, etc.
These differences make a big impact on users, and how they build their websites.
In wordpress its easy to install and easy to use and beginners friendliness
WordPress allows users to change their site’s appearance using themes
WordPress has a strong community of users.
WordPress based websites are often targeted by hackers. However, WordPress is built on a very secure code, and it responds to security vulnerability very quickly.
Joomla installation may not look as quick as WordPress, but it has very similar steps.
Joomla also comes with templates and extensions
Joomla, just like WordPress has a large and very helpful community
Joomla is very similar to WordPress when it comes to security. They actively respond to any security vulnerability and are very quick to patch it up
Drupal’s installation is similar to both Joomla and WordPress. Simply download and upload the package and run the installation script.
Drupal has the same issue with the availability of themes and modules
Drupal has a very proactive community of fans and users.
Drupal takes a very serious approach to security. They publish security vulnerabilities on their own site as they are discovered and patched.