The red wavy line ranges are for AC voltage; the black dash/dotted line ranges are for DC voltage. Those symbols (the wave and the dash above dots) are quite common.
It sounds like you're applying the multimeter properly, but it's not giving you reasonable readings. (The decimal points typically would be turned on and off by the control knob setting, so that part wouldn't bother me too much.) There are a few easy things to check as to why it's malfunctioning: first, maybe the battery in the meter needs replacement. Second, if that's not the problem, it might be possible to disassemble the unit and clean the big switch on the front; sometimes they're pretty easy to take apart, being a few metal contact fingers on the knob and some arcs of traces on the PCB underneath, and cleaning them might restore proper function. Third, if the readings are consistently offset from reality, it may be possible to calibrate the meter against a suitable calibration source if it has some sort of a calibration adjustment internally. That, of course, is assuming that it's working otherwise.
I might also check that the leads and jacks are sound and making good connections. You can check the leads by shorting them on the lowest 200? resistance range; they should read at most a fraction of an ohm. That test, of course, assumes the meter is somewhat accurately metering.
