Laminar and turbulent flows are the two major forms of fluid flow, with laminar flow being an orderly flow with all the fluid molecules moving parallel in the direction of flow, whereas in turbulent flow, different streams of fluid form eddies and unpredictable currents in a different direction than the overall direction of flow. Which type of flow arises in a fluid depends on its speed relative to its viscosity and the size and shape of the pipe or other channel carrying the fluid. Viscosity is the resistance to flow, and more inherently viscous fluids are more resistant to turbulence.
Laminar flow is very desirable for most applications. Laminar flows are much less viscous, or resistant to flow, than turbulent flows. When using forced air or water applications, for instance, it is much easier to pump the fluids at lower speeds that produce laminar flows. Laminar flows actually produce identifiable layers in the fluids that all follow the same path. Making sure a flow is laminar requires slower fluid speeds, smaller, smoother pipes, or some combination of these two.
Turbulent flows require more energy to push because much of that energy is diverted into the secondary currents from the turbulence.