I've been trying to fully understand energy density in terms of the equations that explain it. Unfortunately, the internet hasn't been very helpful in clarifying my misunderstanding. One website defines energy density(u) as energy(E) over volume(V):
I also noticed that pressure(P) can be defined in the same way:
This leads me to believe that they must be describing the same thing. However, I doubt my sources and my own basic knowledge of physics.