Objects that are given by names and contain data used by at least one, usually multiple applications are called environment variables. Put simply, an environment variable is nothing more than a variable that has a name and a value.
Values of environment variable could be the default editor that will be used, for example, the location of all files that can be executed in the system or local settings for the system. Beginners of Linux will find this a little difficult but the environment variable is an excellent way of sharing the configuration settings between several applications and processes.