To delete things in the file system, you normally use a command like "del", which is an alias and points to Remove-Item in PowerShell:
You can use del to delete a variety of things:
Delete a variable named "test":
Delete a function named "test":
Delete an alias named "test":
Delete a registry key named HKEY_CURRENT_USERTest:
You should remember to use the -force parameter if the item you want to delete is write-protected.