You have one copy of data (the data that needs to be backed up), and you have two additional copies of that data (the "3" in the strategy), where one of the backup copies is stored offsite (the "1" part), which naturally follows that it satisfies the middle "2" also.
For over a decade we used 4-3-2 strategy, but it got expensive fast and due to ever evolving budget cuts, our (local gov) customers weren't ready to pay the extra.
There's also 3-2-1-1-0, but that's just a fancy way of saying you _really_ should be doing those restore tests you never seem to have the time, because ransomware can and _will_ corrupt your backup copies.
edit: the absolute minimal setup that still satisfies the 3-2-1 rule: 1) you have your data in production directory on local NVMe stick inside your computer, 2) you copy the original production data to another directory inside the very same NVMe, 3) you occasionally manually copy the production directory data to USB and store that USB inside the shed in your backyard. - That's it. Now your home data is covered by the coveted "3-2-1" enterprise ready backup strategy.
