In a windowed GUI, the window that is currently active is said to have "focus"
In a windowed GUI, the window that is currently active is said to have focus. This is the window to which most keystrokes are sent if the user types something on the keyboard. Clicking on another window will normally transfer focus to that window (and usually bring it to the foreground if it was partly covered by another window). In some configurations, a window may receive focus when the mouse pointer is simply moved onto it.
Focus can also be transferred using keyboard shortcuts such as Alt+Tab
Sometimes a non-selected window pops to the foreground and becomes the window with focus; this is referred to as stealing focus.
