A panel is an area in the Desktop which allows you to run applications (browser, word processor, etc) and perform other tasks. While the panel can be hidden, collapsed, or moved, there should be at least one somewhere on the desktop.
Is the panel gone or are icons missing? First determine whether the panel is missing or whether the panel is there and some (or all) of the icons are missing. If the panel is visible, you can add back missing icons like this:
Has the panel been hidden along the desktop edge? If "auto hide" is selected in the panel configuration, the panel will slide out of the way to leave more of the desktop clear. Panels which are hidden this way will pop up when you move the mouse to the very edge of the screen where the panel has gone from view. To "find" a panel which is on auto hide, slide the mouse slowly along the extreme bottom and top of the desktop. If no panel pops up, try doing this to both of the sides.
Has the panel been scrolled up? If "show hide buttons" is selected in the panel configuration, there will be small buttons at the ends of the panel which "roll" the panel out of sight into a small bar when clicked. Look for a small button that you can click to unroll the panel.
Change panel behavior. Once the panel is visible on the desktop, right click on it and select properties to change how the panel behaves. For example, you might want to switch autohide on or off.
Want to know more about panels? These instructions cover only the basics. For additional information about the desktop panel setup, right click on a panel and select "Help"