The Panel is an area, often along the edge of the screen, which can contain program launchers, menus, the window list and notification area, and other applets.
GNOME by default has two panels on the desktop, one up the top of the screen and one down the bottom. The top panel contains some menus to the left, for Applications, Actions and Places, a notification area to the right, and a clock to the left of the notification area. The bottom panel contains a button on the left which hides all visible windows, displaying the desktop, a window list to the right of that, which contains buttons for all windows open on the desktop, and to the right of the panel a desktop pager.
Panels can be customized in a number of ways. It is possible to change their appearance slightly, to change their contents, and to change their position, size and behaviour.
Contents of Panels
The contents of panels are all applets, which can be added, moved and removed on the panel.
To move applets on the panel, right-clicking the applet in the appropriate area will open a context menu which contains options such as to Lock to Panel, Move and Remove from Panel. To move the applet, select Move and the applet will follow your mouse as you move it along the panel, changing its position. You will notice when moving applets around, the applet will flip to other sides of other applets, or move those applets out of the way if necessary. By right-clicking an applet and selecting Lock to Panel, the applet will not move around for other applets, and will be locked in position on the panel. If you are unable to move an applet on the panel, it might be because it is locked to the panel. Clicking the option from the context menu will deselect this option, allowing you to move the applet. Also note that you must sometimes click on the appropriate spot on the applet. For instance, right-clicking on an entry in the window list will open a context menu related to the window represented by the button (i.e. Close, Maximize, etc.). In the case of the window list, notification area, and some other applets, the right place to click is a small area to one side of the applet.
The Remove from Panel option under the context menu for applets will remove the applet in question from the panel completely. It can be returned at any time. Sometimes however, preferences related to the applet can be lost when removing them from the panel.
To add an applet to the panel, right-click on an empty space on the panel. Empty space might be hard to find sometimes i.e. the window list, when empty, looks like empty space, but is not, so watch out for this, and move / resize / remove applets if they get in your way. The context menu that appear will provide you with an option to Add to Panel. Selecting this will open a dialog which lists many applets that you can add, and their descriptions. They will be placed on the panel roughly where you right-clicked to open the context menu, and you can move them around and change them at will.
Sometimes when clicking on applets special options appear that are specific to that applet. These can provide options and preferences for that applet that you can change, for example, on their behaviour and appearance. You can experiment with some applets to see how you can customize them.
Appearance and Behaviour of Panels
The appearance of panels can be changed in ways by right-clicking on an empty space on the panel to open a context menu, and selecting Properties. Under the Background tab, it is possible to change the background colour of the panel, to provide a background image which will be repeated across the panel, or to change the transparency of the panel.
The size and position of panels can be changed by opening the Properties dialog, and looking under the General tab. Orientation changes which edge of the screen the panel sits on. It is possible for it to sit horizontally on the top or bottom of the screen, or for it to sit vertically on the left or right. It is possible to change the height or width (depending on the orientation of the panel) of the panel by changing the Size option. Selecting or unselecting Expand will determine whether the panel expands to fill an entire side of the screen or whether it is only as big as its contents. Autohide will hide the panel, and make it reappear when your mouse hovers over the appropriate edge of the screen. Show hide buttons determines whether there are hide buttons on the panel, which you can click to make the panel appear or disappear.
It is possible to change the side of the screen a panel is on by clicking on an empty space on the panel and dragging it. When the Expand option for the panel is not set, it is possible for the panel to occupy parts of the screen other than the edges.
Adding or Removing Panels
It is possible to add a new panel by right-clicking on an empty space on an existing panel to open the context menu and selecting New Panel. This will create a new panel on another side of the screen, which you can change around however you want. You can delete an existing panel by selecting Delete this Panel from the context menu.