E = Electronics - variable RPM
B = Brake - an electronic brake that stops the machine from spinning in a couple of seconds.
Q = Quick (release?) - means it has a plug-it cord instead of a permanently attached cord.
Ok, the R, that's a new one and not yet seen beyond the TS 55 R so I'll have to speculate a bit, but if I read the German Festool site they seem to use the word "Randnahe" rather prominently as their big selling point for this new saw, and Randnahe means "near the edge". One of the biggest improvements on this saw is the possibility that it can cut only 12 mm from an edge, so that's what I think the R might stand for. Only speculating though.
And before we get that question, TS = Tauchsäge = plunge(-cut) saw.