What happens when a pilot has no Instrument Rating and visibility drops? Note: I'm not a pilot, so I don't have much basic knowledge of how the pilot licence ratings work

If a pilot doesn't have an Instrument Rating, and the weather conditions drop below VMC; what do they do?

Presumably you can't instantly land, but nor can you safely continue to fly without sufficient visibility?

I know the basic licence includes some instrument training, but is this enough to fly and land without visibility? I was under the impression that was the entire point of gaining an Instrument Rating... To train the pilot to fly on instruments alone
It is very rare for weather to go IMC unexpectedly.

A responsible pilot should see that weather is deteriorating, and begin planning for the nearest available landing.   If they cannot find a landing, they should contact ATC while still in VMC, declare an emergency, and begin working with ATC to get down safely.

In some cases, a pilot may inadvertently enter IMC unexpectedly.   The standard procedure is to execute a standard rate 180&deg; turn, and fly equal time in the opposite direction.  That should get them back to VMC conditions. 

If that doesn't work, unfortunately inadvertent flight into IMC is a leading cause of GA accidents, especially CFIT (Controlled Flight into Terrain - i.e. 'aircraft flew into the ground').   Because of that, even basic private pilot training includes more basic instructions on instrument flying (BAI) than it used to.