We don't even understand why matter has mass.
We don't understand exactly what the force fields are (em, strong, weak, gravity), and why they interact with certain matter at a distance.
Think about, we call it a field, because it is a region in which some force exists that can apply a force to matetr without actually being matter itself.
Those fields have no mass, no matter, are invisible (foreget photons for now)...yet they have the power to "move mountains" of matter.
We know like charges repel, but we don't know why. etc etc
The strange thing is that we have this same lack of understanding in most every field of work, including medicine and drugs for a great example.
These guys are making pills that create certain effects and don't have a clue as to why.
Physics is just one of many.....????????