here is a bit of into Fill mode and align
My advice… if you don’t have Stacks 3 get it now! Learn about making responsive sites as well as the terms in your question. Get some free stacks to learn with and have a good understanding of “responsive” (as well as what you ask about) before you get too seriously into making production pages…
There are many good 3rd party people that offer free stacks as well as paid ones. As you learn be sure to check your work on mobile devices (phones especially). That is very important.