The purpose of Webmentions is to help standardise and facilitate the kind of reactions or interactions you may be familiar with on social media platforms such as comments, shared links, replies and likes.
Webmentions work by operating on the basis that whatever interaction you're sending is stored on your own website and then received by the intended recipient as a notification. The recipient can then either accept or reject to have the contents of your interaction displayed on their own website in a format of their choosing.
Webmentions aren't tied to any particular platform or technology so they can be used in a range of different CMS and programming languages. If you're just getting started with learning how to setup a website then it's worthwhile considering whether one or the other might make it easier for you to send and receive Webmentions. As an example the IndieWeb community has created a PHP-based plugin for WordPress which already facilitates Webmentions.
See our guide to Implementing Webmentions to see which kind of approach best matches your website's setup.