Clarified sticky keys docs.

include/GLFW/glfw3.h

@@ -1741,13 +1741,16 @@ GLFWAPI int glfwGetInputMode(GLFWwindow* window, int mode);
  *  enable sticky keys, or `GL_FALSE` to disable it.  If sticky keys are
  *  enabled, a key press will ensure that @ref glfwGetKey returns @ref
  *  GLFW_PRESS the next time it is called even if the key had been released
- *  before the call.
+ *  before the call.  This is useful when you are only interested in whether
+ *  keys have been pressed but not when or in which order.
  *
  *  If `mode` is `GLFW_STICKY_MOUSE_BUTTONS`, the value must be either `GL_TRUE`
  *  to enable sticky mouse buttons, or `GL_FALSE` to disable it.  If sticky
  *  mouse buttons are enabled, a mouse button press will ensure that @ref
  *  glfwGetMouseButton returns @ref GLFW_PRESS the next time it is called even
- *  if the mouse button had been released before the call.
+ *  if the mouse button had been released before the call.  This is useful when
+ *  you are only interested in whether mouse buttons have been pressed but not
+ *  when or in which order.
  *
  *  @sa glfwGetInputMode
  *