In an actual scenario will the action attribute contain the address of the web server where we want to send our data to?

I can't completely answer this question, but I can at least give some info. When you get into some of the php courses, you'll actually set the action attribute to be the same page you're working on. You are then able to access that information with functions and variables. When doing this, we actually set up to use phpmailer which automatically sent an email with the info from the form. Didn't work when we were just using the page off our localhost, but once we put it on a live server, it did. I was pretty excited to receive an email with my dummy contact form info. :-)

I would think that once you start trying to submit the info to a database like SQL on the server that the action attribute would reference that database, but not the server. I feel like if your code (which any can see) would reference your actual server, that could be a security issue.