What is a Analytics Application? from Google
ga() is tracking snippet. It's implemented as a javascript global function known as the command queue
If the ga() command queue receives a command it doesn't recognize, it simply ignores it, making calls to the ga() function very safe, as they will almost never result in an error.
If a cookie does not exist for the specified domain, a client ID is generated and stored in the cookie
https://developers.google.com/analytics/devguides/collection/analyticsjs/command-queue-reference
In google analytics, an Organization has several account:
When you associate a site with a property, clicking a link to Google Analytics from Search Console will take you to that property’s default view.
Hierarchy of organizations, accounts, users, properties, and views