Air Law and Visibility
The first thing to say is that it is important to ensure that you are studying using an up to date source. It appears that you may not be doing so.
The ICAO minima that determines VMC is 1500 metres, VFR minima is also 1500 metres.
Countries (states) can chose to restrict their pilot licence privileges further. The UK used to restrict the PPL to a minima of 3K and the NPPL to 5K and always to be in sight of the surface. Since EASA this is no longer the case.
Licence privileges are now aligned with the ICAO minima (EASA is compliant with ICAO in this regard).
So flight below 3000ft and 140kts;
VMC minima 1500 metres
VFR minima 1500 metres
CPL/PPL/NPPL minima 1500 metres
When the meteorological conditions are below 1500 metres then the condition is IMC and only flight in accordance with IFR is permitted.
VMC, VFR and PPL privileges within controlled airspace will vary according to the class of airspace.