Bernoulli's principle can be explained by considering the conservation of energy. As a fluid flows, its total energy remains constant. This total energy is the sum of the fluid's kinetic energy (the energy of motion) and its potential energy (the energy due to its position).
If the pressure of a fluid decreases, its potential energy decreases. This decrease in potential energy must be balanced by an increase in kinetic energy, so the fluid's speed increases.
Bernoulli's principle has many applications in engineering and everyday life. For example, it is used to explain why airplanes fly, how sailboats move, and how water flows through a pipe.
