• The title bar appears at the top of the window.
  
  
• The title bar usually contains the title of the program, and a few buttons.
  
  
• When the title bar is blue, this means that this window has 'focus' -- that is this window is receiving whatever keystrokes and mouse-clicks you enter.
  
  
• When the title bar is grey, this means that this window DOES NOT have 'focus' -- that is this window WILL NOT receive any keystrokes or mouse-clicks that you enter. If you want to interact with a window with a grey titlebar, first click on the window, anywhere, which will have the effect of giving the window 'focus', and changing its title bar to a blue color.