Do we actually understand what the forces are? I'm not being cheeky.  I'm not looking for a mathematical explanation of how to measure forces. I'm trying to figure out if humans have yet to understand what is actually happening in the space between items (those being the things that are exerting forces on one another).
So, taking gravity as an example, we know how to measure its effects, but do we actually understand what it is? I've seen it explained as a dimple in spacetime, but that's not really much of an explanation since the visualization always involves a plane with a divot into which things are falling (apparently being attracted to some unseen pulling force beneath the dimpled surface). 
I know there's a very famous Feynman interview in which he quite eloquently illustrates the problem with asking "why" questions, but this isn't a "why" question, this is a "what is it" question. In this interview he describes how charged electrons line up to magnify the magnetic force, but again, that describes the effect. I'm trying to figure out what the force actually *is.
I apologize if this seems like more of a philosophical question than a physics one, but the context is analogous to my saying "do we know what light actually is" and the answer is "it's a bunch of photons traveling at a specific frequency etc. etc" I can visualize this explanation. I'm looking for something comparable for "force". 
 A: Gravity is largely unexplained in modern Physics. The explanation we have for the other three forces is that gauge bosons interact with each other as the means of force carrying. Gravity, however, doesn't seem to follow this model and we have yet to discover any evidence of, or implement a proper framework which would handle, the gauge-boson for gravity, the graviton.
Essentially, you either come to visualise the process as the fundamental forces of any given particle 'pushing' on other particles (which I think is precisely the vague description you find insufficient) or to imagine these 'virtual' particles (gauge bosons) being exchanged between 'real' particles, giving them momentum in so doing.
A: The fundamental forces are called so because they aren't "built on" something else which we could simplify out to. The only correct answer to e.g. "what is strong force" is to say "the strong force is and it has these certain effects." It's not "made of" anything or "based on" anything or "the result of" anything. We can describe the forces by their properties and effects, but we can't currently define them as subsets of some more basic and holistic phenomenon.
