Highlight modes are dependent on the file types you are editing. They are useful because they highlight different types of text into different colours. For example it is useful to put all comments into a specific colour. Important language specific keywords can be highlighted in a different colour. Usability wise your brain will then be able to ignore unimportant text and concentrate on important text, simply by colour.
I work a lot with .htaccess files in Ubuntu 16.04, so wanted a highlight mode for .htaccess. Someone has created one and was available for download, called apache.lang. Unfortunately I could not find out how to put this download into the right directory. Here are my instructions.
