Boundary layers are everywhere. We live within the Earth's planetary boundary layer. Airplanes exploit boundary layers to fly. Golf balls have dimples that alter boundary layer characteristics to maximize their flight time. So what are boundary layers?
Airplanes defy gravity. Formula 1 racing cars corner at incredible speeds generating lateral forces up to 4.5 times that of gravity. Yachts can circumnavigate the globe by wind power alone. These incredible feats are all due to the lift force generated by airfoils moving through air. Of course nothing comes for free; for lift, the cost is drag.
An analysis technique or algorithm, in the context of Computer-Aided Engineering (CAE) software, is typically an iterative set of instructions that, when given geometry, boundary conditions and initial conditions, calculates quantities of interest such as velocity and force.