CSS unminify is used to decompress the compressed css code. If you write code at the development time and compress the code and used in the site. If you want to change something in the code it should be difficult to edit on compressed code. Because compressed code we remove all empty space and code formatting are removed. So it's difficult to understand by the humans.
Here you unminify the code and used the code. In the below textbox past the code and get the output of extracting css code.