readme.md: added more info

readme.md

@@ -4,7 +4,11 @@ Victor The Cleaner for Composer
 [![Downloads this Month](https://img.shields.io/packagist/dm/dg/composer-cleaner.svg)](https://packagist.org/packages/dg/composer-cleaner)
 [![Build Status](https://travis-ci.org/dg/composer-cleaner.svg?branch=master)](https://travis-ci.org/dg/composer-cleaner)
 
-This tool removes unnecessary files and directories from Composer vendor directory.
+This tool removes unnecessary files and directories from Composer `vendor` directory.
+
+The Cleaner leaves only directories containing the source files needed to use the libraries.
+These are located according to the [autoload section](https://getcomposer.org/doc/04-schema.md#autoload) of `composer.json` in each installed library.
+Conversely for example, tests are files that are not needed for use, so they are removed.
 
 Installation
 ------------
@@ -13,20 +17,24 @@ Installation
 composer require dg/composer-cleaner
 ```
 
-Then simply use `composer update`.
+Then simply run `composer update` or `composer require ...` and the Cleaner automatically removes unnecessary files when new libraries are installed.
 
 
 Configuration
 -------------
 
-You can also specify paths to be ignored (ie they will not be deleted) via `composer.json`:
+Some libraries also requires other files/directories, which the the Cleaner judged to be unnecessary.
+In this case, you can list them (specify paths to be ignored), in the configuration and the tool will keep them.
+Or you can specify that some libraries should not be cleaned at all.
+
+Simply add a `extra > cleaner-ignore` section to `composer.json` file:
 
 ```js
 {
 	"extra": {
 		"cleaner-ignore": {
 			"slevomat/eet-client": [  // name of package
-				"wsdl*"               // files or subdirectories, you can use wildcards `*` and `?`
+				"wsdl*"               // list of files or subdirectories, you can use wildcards `*` and `?`
 			],
 
 			"mpdf/mpdf": true         // ignores whole package