A PowerShell profile is a saved collection of settings for customizing the PowerShell environment. There are four types of profiles, loaded in a specific order each time PowerShell starts. The following sections explain these profile types, where they should be located, and the order in which they are loaded.
The All Users Profile
This profile is located in %windir%\system32\windowspowershell\v1.0\profile.ps1. Settings in the All Users profile are applied to all PowerShell users on the current machine. If you plan to configure PowerShell settings across the board for users on a machine, then this would be the profile to use.
The All Users Host-Specific Profile
This profile is located in %windir%\system32\windowspowershell\v1.0\ShellID_profile.ps1. Settings in the All Users host-specific profile are applied to all users of the current shell (by default, the PowerShell console). PowerShell supports the concept of multiple shells or hosts. For example, the PowerShell console is a host and the one most users use exclusively. However, other applications can call an instance of the PowerShell runtime to access and run PowerShell commands and scripts. An application that does this is called a hosting application and uses a host-specific profile to control the PowerShell configuration. The host-specific profile name is reflected by the host's ShellID. In the PowerShell console, the ShellID is the following:
PS C:\ $ShellId Microsoft.PowerShell PS C:\
Putting this together, the PowerShell console's All Users host-specific profile is named Microsoft.PowerShell_profile.ps1. For other hosts, the ShellID and All Users host-specific profile names are different. For example, the PowerShell Analyzer (www.powershellanalyzer.com) is a PowerShell host that acts as a rich graphical interface for the PowerShell environment. Its ShellID is PowerShellAnalyzer.PSA, and its All Users host-specific profile name is PowerShellAnalyzer.PSA_profile.ps1.
The Current User's Profile
This profile is located in %userprofile%\My Documents\WindowsPowerShell\profile.ps1. Users who want to control their own profile settings can use the current user's profile. Settings in this profile are applied only to the user's current PowerShell session and doesn't affect any other users.
The Current User's Host-Specific Profile
This profile is located in %userprofile%\My Documents\WindowsPowerShell\ShellID_profile.ps1. Like the All Users host-specific profile, this profile type loads settings for the current shell. However, the settings are user specific.