①env is a shell command for Unix and Unix-like operating systems. It is used to either print a list of environment variables or run another utility in an altered environment without having to modify the currently existing environment. Using env, variables may be added or removed, and existing variables may be changed by assigning new values to them.
②env file. It's actually a simple configuration text file that is used to define some variables you want to pass into your application's environment. This file needs a something like a parser to make it work. The parser reads the variable definitions one-by-one and parses them to the environment