Bernoulli’s equation relates the speed of a fluid at a point, the pressure at that point and the height of that point above a reference level. It is an application of work-energy theorem in the case of fluid flow.
P1 + ρgh1 + ½ ρv1² = P2 + ρgh2 + ½ ρv2²
P + ρgh + ½ ρv² = constant
P = pressure
ρ = density of liquid
g = acceleration due to gravity
h = height of above the reference level
v = velocity of the fluid