How to do system backup

[mahesh]

Hi everyone, Ubuntu newbie here!

I installed Ubuntu 20.04.2 LTS and I'm starting to dig OS. I installed programs I need to do some work, mounted additional SSDs, personalized system a bit etc., and now I feel comfortable using it.
I would like to have a local backup in case I mess something up while learning all the stuff.

What are my options for creating system backup and what will backup affect?

Thank you!