The terms caver and spelunker are often used interchangeably today, however there is a difference. So much so that cavers used to take offense to being called spelunkers. A spelunker enters a cave for recreational, touristic purposes while a caver explores the cave for professional, geological reasons. So if you are wondering about the difference between caving vs spelunking, one is recreational and the other is usually for scientific purposes.
Today I don’t think spelunking is used as much and both terms have kind of merged into one. At one point though, professional cavers did not like to be lumped together with the amateurs. Many may still not but I think it may not be as big of a deal as it once was.
The term spelunking came about in the 1940s and is derived from the Latin word spelunca meaning a cave or cavern. It was thought to have originated in New England and as I mentioned above refers to the act of exploring a cave as a tourist. A spelunker is not going to be rappelling into a deep cavern with tons of expensive gear like a caver would, but rather leisurely walking around and exploring bit.
A caver may be geologist or someone more serious about exploring caves. That person might have all of the necessary gear required to explore deep into a cave and study the rocks and environment within the cavern. This may involve surveying a mapping out the passageways and rooms of a cave.
This is the actual meaning of caving. However when many people hear the term caving they think of an extreme sport, kind of like “underground rock climbing”. In my opinion the “extreme caver” would fall somewhere in between these two definitions. They are not total novices and are most likely doing some serious exploration with professional gear, however they are doing it for mostly recreational purposes.