Their effects are well known. Exactly what they ARE is matter of considerable conjecture and disagreement.
If you knew even half of what you think you know, I'd still give my cat 3-1 odds in a game of "stump the dummy" in a head-to-head match.
I may not have the time to finish this, but, as I have spent the better part of my life building devices of various function that use or convert EM waves of many differing frequencies from DC through Ku band - I cannot simply let this slip by without at least wading in (again, I may not be able to stay long owing to other commitments on my time.).
These devices have ranged from intimate work on the testing of GaAs semiconductor 'chips' or MMICs to ferrite 'isolators' that support "one way power flow" in wave guide to power levels at and over 100 watts per 'device' in RF power transistors used in VHF power amps designed for amatuer service.
The control, routing, detection, amplification of RF/EM energy via devices - to the 'launching of EM waves into the ether via various antenna technologies is also a technological area of not some small accomplishment. Here, too, electric and magnetic 'field' understanding and is helpful in designing - or troubleshooting an existing design ...
Electricity and Magnetism are well known."Manifestations of the actions of electrons or electron flow."Exactly what they ARE is matter of considerable conjecture and disagreement.
Static magnetic fields in magnetic materials aside (we can discuss those later), one (electric or magnetic fields/force) cannot predominate without the other, They are, therefore related and furthermore, interrelated. Electrons, also possesing 'spin' thereby also exhibit definite magnetic fields, in fact, this is what give magnetic materials their properties - those properties can also be modified of taken advantage of depending on the device, it's application and the material ...
So, where do we go from here ...