Help understand Google Analytics implementation on Web, IOS, and Android

I have a project where I need to use Google Analytics and implement Google Analytics into our web and mobile applications from scratch. I am looking to get a crash course on the practical implementation of Google Analytics in the context of my web and mobile apps.

What I'd like your assistance with is to help me understand:
How Google Analytics works
How I should use it
What I need to consider to implement Google Analytics
What is an effective way to start implementing Google Analytics

Deliverables: There are no deliverables except answering my questions and explaining what and how Google Analytics works and what are the first steps I should take to implement this.

If this is something you can help with, I'd be happy to discuss this further over a call. Please let me know.