SendWinX is a semi-background mode. If the target window is in the background, SendWinX activates it without bringing it to the top of the Z order.
SendWinX's advantage over the true background modes (SendWinM, SendWinMF, SendWinS, and SendWinSF) is that SendWinX handles shifted and unshifted characters correctly.
You will probably want to use Restore at the end of a hotkey that uses SendWinX to give focus back to the foreground window.
SendWinX uses the operating system command SendInput.