This is the area on the bottom right of your screen next to the time. There are icons here that represent some of the programs that are running in your computer now. You may only see a few of them with an arrow on the left margin of the tray (an UP arrow in Win7). If you click on that arrow, the number of icons displayed will momentarily increase.
If you see a lot of icons in the system tray, it’s probably not a good thing. It means there is a lot going on and most of it may not be of much value. If you park your mouse over the icon for just a few seconds a flag will pop up telling you what the icon represents. If you right-click on the icon, you probably will see a menu pop up which will allow you to exit that program or otherwise manage the application. Double clicking (single click in Windows 7) on the clock will pop a window with the time of day and a calendar. You can also check to see if your computer is set to the correct time zone and other characteristics.