There are three ways to invoke a script by PowerShell.exe. Assuming a script is in the current directory, they are:

    PowerShell -Command .\Script.ps1
    PowerShell -Command . .\Script.ps1
    PowerShell -File Script.ps1

The first command invokes a script in its script scope which is a child of the global. The script mostly does not affect the global scope unless it explicitly requires this in some commands or uses the prefix global for scoped items. Mostly, because some automatic variables still may be changed.

The second and third commands invoke a script in the global scope, that is the script scope and global are the same. In other words, if a script creates or changes things in its scope then these changes are global.

In some cases changes in the global scope may cause different results and program flow. For example created global aliases may conflict with script module functions, see Conflict-with-aliases.

Scripts

• MyScript.ps1 defines some items in the script scope and tries to get them as global.
• Test-1-Command-normal.ps1 invokes PowerShell .\MyScript.ps1, it gets nothing, i.e. the defined items are not global.
• Test-2-Command-global.ps1 invokes PowerShell . .\MyScript.ps1, it gets the global items defined by the script.
• Test-3-File-global.ps1 invokes PowerShell -File MyScript.ps1, it gets the global items defined by the script.