How are boundary conditions in Matlab's example 'Heat Distribution in a Circular Cylindrical Rod' obtained?

I am trying to understand the example 'Heat Distribution in a Circular Cylindrical Rod' available at http://uk.mathworks.com/help/pde/examples/heat-distribution-in-a-circular-cylindrical-rod.html. I understand the that the outer boundary condition is a Neumann boundary condition for convention at the boundary. What I don't understand is how the syntax of the values of 'g' and 'q' are build up. Essentially what are 'thePde', 'loc', 'state' and 'loc.y' and why the values 50 and 50*100? the lines I am referring to are: outerQ = @(thePde, loc, state) 50*loc.y; and outerG = @(thePde, loc, state) 50*100*loc.y;