"20db" cuts the output down by 20db. 1/10
"INV" inverts the output--------_------- now looks like_________-_______
Frequency range question: Probably it can make 0.2hz to 2mhz with good distortion. It can make a slightly larger range but can not meet some specification.
DC offset; if offset o= then a sign wave of 2V peak to peak will give you -1V to +1V. With an offset of 5 volts it will give you 5V to 6V.
"Pulse out" is a output that normally you can not set the voltage. (fixed at 5 volts or 1 volt) It is square or sign it is just a pulse at the same frequency at the main output.