WordPress is a content management system (CMS) that enables you to create a website or blog from scratch, or to improve an existing website. WordPress is free and open source software released under the GPL. WordPress is a blog-focused CMS, while Drupal is more suitable for websites with more complex design requirements. WordPress also has a larger community of users and developers than Drupal.
However, Drupal is more comprehensive and can be used to power larger websites. In the end, it comes down to what you need WordPress for – if you need a blog platform, WordPress will work well; if you need a more comprehensive platform, Drupal will be better suited.