The difference is if you press esc the "respawn" button is highlighted and availible to click on the "please wait" screen. (I think the game basically thinks you are in an "unconsious" state but I'm just speculating)
On rare occasions the screen gets stuck on "please wait" while logging in, if you are patient this should eventually (after 40-120secs) either log in or auto disconnect (which is safe and wont lose you your character.)However I have on one occasion been glitched on this screen while logging in (I know it was glitched cos the screen went blue instead of the usual black and I waited 3mins with nothing happening) and I lost my save when I exited.