First one is window activation following mouse cursor. For example - when having two notepad windows open on single virtual desktop and writing in first one, then moving mouse cursor over second window should activate it and enable you to type text there.
Second feature is *not* raising windows to the top upon such an activation, raising windows should still be possible by clicking on application title bar, borders or through alt+tab switcher/taskbar.
Those features are ones I miss most from xfwm4 (XFCE desktop environment window manager). Together they enable fluent work and switching between windows without distrupting their order. It's a kind of second step of "always on top" feature.
Edit: Great thanks for changing window manager in windows into something usable
