The Charms Bar can be seen in the screenshot below. This is a new feature of Windows 8 brought about primarily because Windows 8 is meant for a touch screen type of pc. (Although a regular pc with a keyboard and a mouse can also bring the Charms bar up, as will be described.)
The name of the Charms Bar probably was chosen because the icons for them on the bar are similar to what you might see on a charm bracelet. The Charms Bar will be capable of being raised either on the Start screen, the Windows Store apps (which used to be called Metro apps), or the Desktop. But they may not be relevant to whichever place the bar was brought up.
You can raise the Charms Bar with a keyboard, or your mouse, or a touch screen. I actually raised them with a mouse because I put Windows 8 on a regular desktop pc and on a regular laptop.
If you use a mouse, then you must begin by moving the mouse cursor to either the top right corner of the screen or the bottom right corner of the screen, and then move it (either up or down) towards the center of the righthand edge of the screen. (Probably making this double motion of the mouse is necessary for invoking the Charm Bar in order to ignore any normal mouse maneuvers to the right edge of the screen.) After you then move the mouse down (or up) along the righthand edge of the screen, you will see something like the screenshot below:
If your pc has a keyboard, you can use the shortcut Windows Key and C held down at the same time. Or, finally, if you have a touch screen, then you use a swiping motion of your hand from the righthand edge of the screen towards the middle of the screen.
As you can see from the screenshot above, the five charms on the Charms Bar are, from top to bottom: Search, Share, Start, Devices and Settings.
Now I'll describe the use of each of these charms.
The Search Charm either has global application, or context sensitive application, depending upon where you invoke it from. For example, invoking from the Desktop or the Start screen causes it to search the entire system, and you can search for settings, files or installed apps. This is depicted in the next screenshot, below:
Invoking the Search Charm from the Windows Store will give you the chance to search it for apps, as depicted in the screenshot below:
Other Windows Store apps, such as Windows Mail, might have their own capabilities of search, which would be accessed in the same way. The Search Charm may be invoked by holding down the Windows key and the Q key simultaneously.
The next Windows 8 Charm, Share, will only function when you access it from within a Windows Store (Metro) app. These apps use what are called "share contracts" in order to be able to share data. For example, you could have a web page visible in Internet Explorer, and if you wanted to be able to send that page to someone you know via email, then you would take advantage of the share contract between Internet Explorer and your email client. This is shown in the next screenshot:
You can bring up the Share contract if you use the keyboard shortcut: Windows Key and H
The Start Charm has a quite simple function: take you back to the Start screen. If you were previously already on the Start screen, then you'll be brought back to whatever other Windows Store app (or the Desktop) that you were using. You can also invoke this Charm with a keyboard shortcut of holding down the Windows key.
The Devices Charm mostly is applicable to use within the Start screen or Windows Store (Metro) apps. For example, you might want to print something from a Windows Store app, in which case you would invoke this Charm. Or, if you have multiple monitors connected to your pc with Windows 8 on it, you could use the Devices Charm to deal with them. The next screenshot shows an invocation of the Devices charm from the Maps app.
You can invoke the Devices Charm with the keyboard shortcut of Windows Key and K.
The last Charm on the Charms Bar is the Settings Charm. It has both global settings and those that are sensitive of the context from which it is invoked. At the bottom of the Settings Charm you see some system-wide settings, such as the Power option where you can choose to Shut Down, as well as options for how the Network operates, the Sound Volume, Brightness -- a slider that is marked as Unavailable on my desktop pc, since it is available only on laptops and touchpads, Notifications, and Keyboard. Screenshots are included below for settings of the Power button, Network settings, Sound volume setting, and Notifications settings.
The settings you see at the top of the Settings pane are sensitive to the context from which you invoke it. If you invoke from a Windows Store (Metro) app, you will see that app's settings. A screenshot is included below which shows the Travel app's settings.
If you invoke it from the Desktop, then there is a link to the Desktop Control Panel. If, on the other hand, you click on the Change Pc settings link at the bottom of the pane, then you get the Settings for the Windows Store (Metro) apps.
You can use the keyboard shortcut Windows Key and I to invoke the Settings Charm.