Building your first website is an awesome experience! There are mostly two kinds of websites, static and dynamic. Static websites are made of content that doesn't change, its always the same. In dynamic websites, the request is processed by a programming language for creating a response, and the output can be different depending on anything you want.
For a dynamic website, you would also need a programming language, I would recommend Python.
A CMS (content management system) like Wordpress is a website of the second class, written in PHP. The easiest way to get up and running is using a hosted solution provided by a 3rd party, for example wordpress.com. They take care of the website administration and you only care about the content. Customizing the looks of a wordpress site is well documented.
It is possible to install wordpress or other CMS yourself, it is challenging and requires system administration knowledge level. A challenge like this one would teach you a lot of tricks and the inners about Linux.
For each of the solutions I described, you will likely need to learn HTML and CSS. So I would start there. Using a hosted solution is probably the easiest. Finally, doing everything by yourself is the hardest, and as usual, the most rewarding.
Thanks a lot for your reply, it's really instructive. I have never seen a static website I think... Do you have a link that can show me what is it?
Thank you in advance