Definitions for "System Tray"
The system tray is a part of your Windows taskbar, located across the bottom of your screen. On the left is your start menu, and to the right is the system tray which contains a clock. Beside the clock are various icons representing certain programs you have open. Unless otherwise specified in the preferences, Trillian places an icon in this area.
Systray.exe is a tool for system taskbar notifications. The taskbar provides a location for programs and hardware devices to display icons.
Windows - Shows you what is running in the background. Lower right corner of the taskbar.