The lecture starts with the concept of continuum mechanics and how a specific constitutive relation--Newtonian fluid--may be postulated to develop the governing equations for general fluid motions--the Navier-Stokes equations. We shall illustrate how this non-linear PDE may be solved after proper simplifications via flow geometry and steadiness or via scaling analysis. Hence, we shall cover continuum mechanics, constitutive relations and boundary conditions, governing equations, solutions to the NS eqns in terms of velocity and pressure, in terms of streamfunction, and in terms of vorticity. We continue with the concept of scaling analysis and how the full NS eqns can be approximated at high and low flow Reynolds number condition. Boundary layer equations will be discussed together with its solution strategies. Low Reynolds flow problems, including the lubrication theory and Stokes' formula, will be followed.