it will be very much helpful if someone explains this given code of CFD toolbox

% QuickerSim CFD Toolbox: Solve a stationary Navier-Stokes problem in 2-D

clc;

clear;

% Read and display mesh

[p,e,t] = importMeshGmsh('cylinder.msh');

% [p,e,t] = importMeshGmsh('naca5418.msh');

displayMesh2D(p,t);

% Convert mesh to second order

[p,e,t,nVnodes,nPnodes,indices] = convertMeshToSecondOrder(p,e,t);

% Define fluid

nu = 0.02;

% Init solution and convergence criteria

[u, convergence] = initSolution(p,t,[1 0],0);

maxres = 1e-3;

maxiter = 25;

% Define inlet velocity profile

vel = [1 0];

% Iterate nonlinear terms

for iter = 1:maxiter

% Compute shear rate and viscosity for non-Newtonian fluids if needed

% gamma = shearRate(p,t,u);

% nu = nuinf + (nu0-nuinf)*(1+(lambda*gamma).^2).^((n-1)/2);

% Assemble matrix and right hand side

[NS, F] = assembleNavierStokesMatrix2D(p,e,t,nu,u(indices.indu),u(indices.indv),'nosupg');

% [NS, F] = assembleNavierStokesMatrix2D(p,e,t,nu,u(indices.indu),u(indices.indv),'supgDoublyAsymptotic');

% Apply boundary conditions

[NS, F] = imposeCfdBoundaryCondition2D(p,e,t,NS,F,10,'inlet', [1 0]);

[NS, F] = imposeCfdBoundaryCondition2D(p,e,t,NS,F,12,'slipAlongX');

[NS, F] = imposeCfdBoundaryCondition2D(p,e,t,NS,F,13,'wall');

% Compute and plot residuals

[stop, convergence] = computeResiduals(NS,F,u,size(p),convergence,maxres);

plotResiduals(convergence,2);

% Break if solution converged

if(stop)

break;

end

% Solve equations

u = NS\F;

end

% Plot solution

figure(3);

displaySolution2D(p,t,u(indices.indu),'x-velocity');