PowerShell is a script automation framework developed and released by Microsoft that empowers system administrators and developers to perform tasks predictably and repeatedly. Originally part of the Microsoft Management Framework for Windows, PowerShell now ships as part of the Windows operating system in both its workstation and server guises.
Similar in concept to the shells that ship with *NIX PowerShell is rapidly becoming the de facto toolset for the management of Microsoft applications and the infrastructure that powers the Microsoft Cloud. Due to its predictable and repeatable nature, PowerShell provides reliable tooling for automation, orchestration and desired state configuration management of on-premises and Cloud infrastructure, services and workloads.
If you’re interested in the history of PowerShell, Jeffery Snover’s (the original “inventor” of PowerShell) 2002 paper outlining his vision for what was at the time called “Monad” can be found here.