Files such as the HOSTS file that appear to be “extensionless” actually contain an invisible period “.” — or dot — at the end the file name. It is this invisible dot that will enable us to select a specific program with which to open files with no extensions.

What is a extension file and how it works?

A file extension, or filename extension, is a suffix at the end of a computer file. ... File extensions are used by the operating system to identify what apps are associated with what file types—in other words, what app opens when you double-click the file. For example, a file named “awesome_picture.

How do I open .less files?