Look at the units of each term in the equation $\dfrac{p}{\rho g} + \dfrac{v^2}{2g} + z = \text{constant}$. Each term has units of length, but multiplying through by weight per unit volume ($\rho g$) turns them into energy per unit volume: pressure energy, kinetic energy and potential energy. Conservation of mass instead gives the continuity equation ($A_1v_1 = A_2v_2$), and conservation of momentum gives the momentum equation used for forces on pipe bends, which are different relations from Bernoulli's equation. Since Bernoulli's equation adds up pressure, kinetic and potential energy terms to a constant, it is the energy balance for the flow.
\[\boxed{\text{Energy}}\]