A Front End developer is the one who designs the websites, and what users see on their end. It includes the basic structure of the website arranging the elements of the page, and styling the website making it look attractive and also user friendly.
Now the structuring, designing and styling of your website can be done using these three programming languages:
1)HTML: Hypertext Markup Language is used to give the basic structure of your website and the elements it will contain. You can add pictures and any user-accessible links with the help of HTML.
You can visit the below link to learn HTML
2)CSS : (Cascading Style Sheets): It is a style sheet language used to style your web page(HTML). It decides the way your website is presented to the user. For example changing the size, font, color of your text and layout of the webpage etc. improves the user-friendliness and visual attractiveness of your website.
learn about CSS from below
3)JAVASCRIPT: It is a scripting language used along with HTML and CSS to decide the behavior of your websites and add behavior to the elements inside the website. It makes the user's experience much better.
Not only in web development, but javascript also has many more applications.
you can learn javascript from the below link
Now that you are familiar with these three languages which are the building blocks of front-end development, you can learn different javascript frameworks like ReactJs and AngularJs.