need help with old receivers tone controls

I have a vintage Marantz 2265 receiver that is used in my study for very low level-nearfield listening. It has a loudness compensation control which I find very useful for extremely low level listening. It also has bass, mid and treble tone controls...and it has a control called tone mode. The indents are labeled out and in which I obviously understand, and the other indents are labeled 100Hz 10kHz 100Hz/10kZ. Are these low, high and combined low high cutoffs of frequency response? There is no manual to refer to and I'd like to know exactly what these cutoffs do and why they were designed into the unit, unless they were a market driven item during the "age of the equalizers".