Let's go, understand the code watching other dev Codepen.io.
Is a collaborative platform for programmers and developers, this programmers your code for public access and other devs have access to the code.
These devs with access to code, understand how its works, and reuse all features it has the code block that runs certain functionality, generally the code focus is a web design, web interactions, animations that can inspire you to learn new methods of build code.
You can also post your codes for other people to find and looking code and testing these codes and run them on your websites
At this moment, the people talk, WOW, like this code and your code it's going to be for everyone, your collaborate with a person that probably its start but does not understand how to work with the language, specifically CSS, JS, HTML
There form differences to work whit the language as it the utilization of preprocessors for automatically code generate or include work with frameworks as react with the JSX syntax. Now is compatible with the codepen online editor and are add frequently new functionalities.
An online code editor is a great option for Jr. Developers because they don't need to install a tool in their local computer, only need an internet connection and foundation in the language to start coding.
Remember, don't copy and paste code if you don't understand the main functionality.
(I learning English, sorry for my grammar)