Why A multimeter is a combination instrument that measures voltage (as a voltmeter), current (as an ammeter) and resistance (as an ohmmeter). Those DC/AC electrical quantities are what the basic analog or digital multimeter is built to read. Resistance is measured with the circuit powered off, using the meter's internal battery to push a small test current through the component.
Watch out Impedance and reactance are frequency-dependent AC quantities that need an impedance bridge, antenna analyzer or vector network analyzer, not an ordinary multimeter; signal strength and noise are measured with receivers, S-meters or spectrum analyzers.
Multi = volts, ohms, amps. If the quantity depends on frequency (Z or X), a multimeter can't see it.