Users accounts vs. alias

[CharlotteAC]

I apologize for this question, but I’m confused about what a User Account can do vs. what an Alias Account can do. I needed to change my email address on my laptop as I’ve switched providers. I figured out how to do that but do I need to add my new alias as a User Account on my laptop? My new alias isn’t showing up yet, may be too soon, but I thought it shared the same password & access as my previous primary account?