Update README.md

Author: chyndman

README.md

@@ -6,24 +6,29 @@ Part of the Elixir on Windows Google Summer of Code 2014 project, this installer
 
 ## Features
 
-* Installs the latest Elixir version, or another version the user selects
+* Downloads and installs the latest Elixir version, or another version the user selects
 * Offers to installer Erlang and add the Erlang directory to the system's Path variable
-* Downloads and extracts the selected Elixir package to your favorite directory (or mine)
 * Adds Elixir to the system's Path variable
 * Creates shortcuts to IEx and the uninstaller
 
+## Structure
+
+The **offline installer** ([Elixir.iss](Elixir.iss)) packages a specific Elixir release to install, and also can append the system's Path variable appropriately.  This kind of installer is currently not distributed in binary form.
+
+The **web installer** ([ElixirWeb.iss](ElixirWeb.iss)) is what's currently distributed (see [Releases](https://github.com/chyndman/elixir-windows-setup/releases)). The **web installer** itself does not install Elixir.  It packages the files necessary to download an Elixir release of the users choosing, build an **offline installer** against this release, and run the resulting **ofline installer** that performs the actual Elixir installation.  It also handles installing Erlang and adding it to the system's Path variable.
+
 ## Build Instructions
 
 First, download the Unicode version of Inno Setup (`isetup-X.Y.Z-unicode.exe` from [jrsoftware.org](http://www.jrsoftware.org/isdl.php#stable)) and install it, making sure to keep the "Install Inno Setup Preprocessor" checkbox checked when asked.  Then, clone this repo (`elixir-windows-setup`) to your system.
 
-To build the web installer (which offers to install any release of Elixir as well as install Erlang), follow these steps:
+To build the **web installer**, follow these steps:
 
 1. Download and install the [Inno Download Plugin](https://code.google.com/p/inno-download-plugin/).
-2. Download the [7-Zip Command Line Version](http://www.7-zip.org/download.html) and extract it to `7za920` in your Documents folder (i.e. `C:\Users\YourUserName\Documents\7za920`).
+2. Download the [7-Zip Command Line Version](http://www.7-zip.org/download.html) and extract it to `7za920` in your Documents folder (i.e. `C:\Users\YourUserName\Documents\7za920`).  You can redefine the `PATH_TO_7ZA` macro if you have this extracted elsewhere.
 3. Open `elixir-windows-setup\ElixirWeb.iss` in the Inno Setup Compiler.
 4. Click "Compile" to build an installer in `elixir-windows-setup/Output`.
 
-To build the offline installer (which installs a specific release of Elixir and nothing else), follow these steps:
+To build the **offline installer** follow these steps:
 
 1. Extract Precompiled.zip of the desired [Elixir Release](https://github.com/elixir-lang/elixir/releases/) into `elixir-windows-setup\elixir`
 2. Open `elixir-windows-setup\Elixir.iss` in the Inno Setup Compiler.