What is Sitecore Powershell Extensions(SPE)?
It is Sitecore accelerator which can drastically increase the speed to develop a Sitecore solution and helps you write script in powerful way. It provides a command line and scripting environment for automating Sitecore tasks.
Is it Licensed tool OR free to download?
If you have Sitecore license, these extensions are free of cost.
How to install it?
You may download it from Sitecore downloads as well.
|Sitecore Powershell Extension Interface|
Why you need it?