Where can I use this?

I have learned the basics of HTML/CSS. So I wanted to make a little webpage, but after searching the web, all I could find were webpage building softwares; which just made them for you. This may be ridiculous, but I was imagining a little window where I could write code, beside another window where my results would be. Where I could choose my domain name and “finish” my site. Does anything like this exist? If not, then why did I learn this language?

Now, i am going to split this question in two parts. part one: writing html + css files on your computer. part two: host your pages on github.

I personally would use something like notepad++ or sublime text to write html + css files.You can view this files in your browser, if you make changes in your files, you can simple refresh teh browser (this will be quick given the fact that the html file is on your computer)

See you can understand this, then we go about hosting pages on github