Layout vs Grid Problem – Graphic Design Stack Exchange

I have trouble understanding the relationship between material layout definitions and the Material 8px grid system. When you place one on the other, they do not fit.

So, why do I use the layout? And for what do I use the gird?

Grid Vs Layout

Moreover, I read about the hard grids and the soft grids, but the difference between them is not very clear. How would you define it?

Thank you!