There are in general three types of fluid flow:-

~Laminar (Streamline)
~Turbulent
~Transient

Laminar flow (other names: Steady, Streamline flow)

In laminar flow, the velocity of moving fluid at any fixed point doesn’t change with time, either in magnitude or in direction.

Laminar flow generally happens when dealing with small pipes and low flow velocities.

Laminar flow can be regarded as a series of liquid cylinders in the pipe, where the innermost parts flow the fastest, and the cylinder touching the pipe isn’t moving at all. Shear stress depends almost only on the viscosity – μ – and is independent of density – ρ .
Example may regarded as The gentle flow of of water near the center of a quiet stream.
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Turbulent flow

In turbulent flow vortices, eddies and wakes make the flow unpredictable.

Turbulent flow happens in general at high flow rates and with larger pipes. Shear stress for turbulent flow is a function of the density – ρ.
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Transitional flow
Transitional flow is a mixture of laminar and turbulent flow, with turbulence in the center of the pipe, and laminar flow near the edges. Each of these flows behave in different manners in terms of their frictional energy loss while flowing, and have different equations that predict their behavior.

Turbulent or laminar flow is determined by the dimensionless Reynolds Number.
The Reynolds number is important in analyzing any type of flow when there is substantial velocity gradient (i.e. shear.) It indicates the relative significance of the viscous effect compared to the inertia effect. The Reynolds number is proportional to inertial force divided by viscous force .

The flow is
Laminar when Re < 2300
Transient
when 2300 < Re < 4000
Turbulent
when 4000 < Re.

Where Re denotes Reynolds' number.