A VSWR of 1:1 means that the coax is presenting a 50 ohm load to the transmitter, assuming the meter is between the radio output jack and the coax input. It doesn't mean that the coax is delivering the power to the antenna, and it doesn't mean that the 50 ohms is purely resistive.
A high (3:1 or higher) VSWR indicates a mismatch between the input to the meter and the output of the meter. It doesn't tell you where the problem is.
A VSWR of zero is impossible. VSWR goes from a minimum of 1:1 to a maximum of infinity:1.
SWR stands for standing wave ratio. It is the ratio of the power of RF going to the antenna vs that reflected back back into the RF amp due to impedance mismatch. Antenna impedance is a function of the total impedance (Resistive, Inductive and Capacitive) of the antenna which is generally a function of antenna length and transmission line characteristics. High VSWR's generally mean one of two things high resistance between the transmiter and the antenna (bad coax) or an antenna whose physical/electrical length is not an even harmonic of the RF wavelength being transmitted.
Cheap CB VSWR meters may not be able to go less than 1 but the tuners we used in the Navy to tune our HF xmitters would. The only time they'd go less than 1 was to indicate a fault - usually a coax connector was shorted out due to seawater corrosion.
I suspect CB antennas do represent a 50 ohm impedance because CB radios generally use RG52 coax. I've worked on a variety of both low power and high power xmitters (like 500,000 Watt HF xmitters at Pensacola NAS and a 50,000 watt UHF TV xmitter at KOKH in OKC) that had impedances from 50 all the way up to 1000's of ohms. One radar I worked on had a xmission impedance well over a megohm.
The point of my original post was that if the VSWR meter was in the bit over 1 range then RF energy was reaching the Antenna and that the antenna was tuned close enough for government work.