What does Euler equation mean?

In order to prove the Bernoulli’s principle ($\frac{p}{\rho} + \frac{1}{2}u^2+\phi = constant$ ), I have to use the Euler equation: $\frac{Du}{Dt} = -\frac{1}{\rho}\nabla p + g$.

I know how to prove it, but I didn't understand what does it mean and say (Euler equation)?

any help appreciated!

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It is not really clear to me what you want to know? Can you maybe clarify a bit? – Bernhard Mar 6 '13 at 21:02
Have you looked at en.wikipedia.org/wiki/Euler_equations_(fluid_dynamics)? – joshphysics Mar 6 '13 at 21:03
thank you both.. sorry for my english.. I give an example: Pythagorean theorem (a^2+b^2=c^2) means that in a right triangle, a^2+b^2=c^2 where: c represents the length of the hypotenuse, and a and b represent the lengths of the other two sides. thank you both! – Alon Shmiel Mar 6 '13 at 21:43