(GH-73) Fill in WIP page for PowerShell

input/en-us/features/powershell.md

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 xref: packaging-for-the-masses
 Title: Packaging for the masses - PowerShell
 Description: At its heart, Chocolatey uses the Windows Automation Language, PowerShell, to perform its different operations
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-> :warning: **WARNING** This is a Work in Progress. Please check back later.
+Released in November 2006, Windows PowerShell, quickly became the defacto way to automate tasks on Windows. Whether it was automating the creation of Users within Active Directory, or configuring/maintaining your Exchange Server, PowerShell was the way to do it.
+
+When Chocolatey started, it was clear that PowerShell was going to be at the heart of how it works as well, and that continues to this day.
+
+Within a Chocolatey package, there are three main PowerShell files:
+
+- chocolateyInstall.ps1
+- chocolateyUninstall.ps1
+- chocolateyBeforeModify.ps1
+
+> :memo: **NOTE** Not all of these files are required within every Chocolatey package, as Chocolatey performs a number of tasks automatically, and overrdiing the dfeault functionality is only required when you want to do something different.
+
+When a Chocolatey package is installed/uninstalled, these files are executed at [different times](xref:create-packages#during-which-scenarios-will-my-custom-scripts-be-triggered), giving a [package creator](xref:create-your-own-packages) full control over exactly what actions are performed within a package.
+
+This flexibility allows for the creation of simple packages (that simply execute a native installer) all the way up to highly complicated installations that perform several operations.
+
+On top of this, Chocolatey ships with a number of [built-in functions](xref:powershell-reference), to help with the specific tasks of installing applications, binaries, zips, and scripts.
+
+When you need to create your own custom PowerShell functions, Chocolatey provides the ability to create [extension packages](xref:extensions), to allow the sharing of code across multiple packages, rather than duplicating it.