This equation is more a "theory of everything we know so far." It's a summary of the standard model of particle physics and general relativity. Unfortunately understanding any given term in the equation requires a lot of background knowledge. Here's the general idea: ##A## and ##F## are related to the electric and magnetic fields and their analogs for the weak and strong force. ##\Phi## is the Higgs field. ##g## is the "metric of spacetime" which you can think of as the gravitational field. ##R## is a measure of the strength of the gravitational field. ##\psi## represents all matter particles such as electrons and quarks. ##V_{ij}## is kind of a table of particle masses. ##W## is the "partition function" which is a tool for calculating things in quantum mechanics.



When people talk about a "theory of everything" they want something that goes beyond what is summarized in this equation: something that resolves certain problems with quantum mechanics and general relativity and explains where the particles and forces that we know about come from.