what is parameter Fx Fy

what is parameter Fx, Fy, ρ  In Featool plane stress equation

If you press in the [?] button in the lower right corner you will be directed to the equation specifications in the documentation. Alternatively, you can press the [edit] button and see how the equations and coefficients defined by the physics mode. Hovering a few seconds over a coefficent edit field also shows a tooltip with a description.