what is Analysis Bandwidth?

[fonograph]

I was looking at the Keysight spectrum analysers and 56k $ spectrum analyser have 23k $ option to upgrade the analysis bandwidth to 85MHz.Is the analysis bandwidth a sort of window that sets the limit at how low and high freqency you can look at the same time?

Does that mean that if I pay 56k for 3.6ghz analyser,I can really only analyze 25MHz at once without the upgrade?

[fonograph]

I think I figured it myself,it only matters if you want to demodulate some signal,it have nothing to do with maximum sweep span.