If you are wondering about "resistance" versus "impedance", then don't fret - it's similar territory ... sort of.
In its
simplest form, "resistance" is a DC measurement and "impedance" is an AC measurement - but they both refer to how they affect the passage of electric current. **
As such, a low impedance power supply will provide a nominal voltage, with the ability to supply high levels of current, whereas a high impedance power supply will not be able to produce a lot of current at all.
Exactly what "high" and "low" mean here is very dependent on the environment. In a power station supplying mains power to homes and industry, a generator with a "high" impedance is no good for that job, but it would almost look like an ideal power supply on someone's test bench. (Mental image here ....
)
** Beginners Section type answer