Azure provides several ways of interacting and automating things. The two main ways to interact with Azure besides the portal are Azure PowerShell and the Azure Command-Line Interface (CLI).
Both are basically just wrappers around the Azure API to enable everyone not familiar with RESTful APIs, but familiar with their specific scripting language, to use and automate Azure. The Azure PowerShell module provides cmdlet for managing Azure services and resources through the Azure API. Azure PowerShell cmdlet are used to handle account management and environment management, including creating, updating, and deleting resources. These cmdlet work completely the same on Azure, Azure Pack, and the Azure Stack, Microsoft's private cloud offerings.
Azure PowerShell is open source and maintained by Microsoft. The project is available on GitHub at the following link: https://github.com/Azure/azure-powershell. The Azure CLI is a tool that you can use to create, manage, and remove Azure resources from the command-line. The Azure CLI was created for administrators and operators that are not that experienced with Microsoft technologies, but with other server technologies, such as Unix or Linux. The Azure CLI is an open source project as well, and is available for Linux, macOS, and Windows here: https://github.com/Azure/azure-cli.