If you're confused about which mode to run PowerShell in, there are some distinct differences and reasons why you would want to run one mode versus the other.

Normal Mode

PowerShell can be run in "normal" mode. Normal mode offers access to the PowerShell console and certain functions but can be far less potentially damaging to the system. Normal mode runs under the non-elevated user context of the person that initiated execution of the console.  Whatever system rights that the currently logged on user possesses, that's how the PowerShell console will work. A non-elevated normal user generally doesn’t have rights to do things like alter printer drivers, read the system's Security log file, or even change the computer's time. So, PowerShell's abilities will be limited, too.

Normal mode is the best mode for PowerShell newbies, ensuring that there is far less opportunity to damage the computer in some way. As you start working with PowerShell and attempt to do things that limited user rights prohibit, PowerShell will give a general warnings like: Access to <name> resource was not available to the client or Cannot open <name> service on computer.

To run in Normal mode, just access PowerShell using the application's icon.

Administrator Mode

Administrator Mode for PowerShell gives the user carte blanche access to the full power of the scripting language because the logged on user has full access to the entire range of the system's components.

To run in Administrator Mode, even if already logged onto the computer as an administrator, you must choose the Run As Administrator option when executing PowerShell. For Windows 7, this involves right-clicking on the application's icon and choosing the option. For Windows 8, just use the Search function, locate PowerShell, and then right-click on the proper result (as shown below).

Administrator Mode is for those who are already comfortable with PowerShell, or for those cases where a particular Cmdlet requires it. For example, the Get-Disk cmdlet requires proper access to local storage, so administrative rights are required.