Why An antenna analyzer is a low-power signal source plus an impedance bridge: it sweeps a frequency range and reports the complex impedance (R and X), SWR, and resonant frequency of whatever is connected to its port. Because coax is just another load at the analyzer's terminals, you can measure a cable's characteristic impedance, electrical length, and velocity factor by testing it open or shorted at the far end. What it cannot do is evaluate radiation properties, since those require measuring fields at a distance.
Watch out Front-to-back ratio and antenna gain are radiation-pattern measurements that need a test range with a distant source and a reference antenna, not a bridge at the feedpoint. Transmitter power output is measured with a wattmeter, and feeding transmitter power into an analyzer can destroy it.
Analyzer sees only what's at its connector: impedance, SWR, resonance. Anything about the far-field pattern needs a test range.