macOS Catalina is here so let the backups begin. Rene Ritchie has the ultimate guide.
You absolutely have to back up your Mac. If you don’t, one day — maybe tomorrow, maybe next week or next year — you will lose something important and irreplaceable and there will be nothing future you can do but curse at and blame past you. I don’t say this to scare you. I say it to save you. Back up. Do it now.
All step by step.