How to clone a volume
Cloning a volume makes an identical copy. Cloning is more than a backup, it’s a functionally-identical copy, a distinction that is particularly relevant for your boot drive (system and applications): you can start the Mac from the clone.
See also Using Cloning as a Backup Strategy.
Cloning with Carbon Copy Cloner
Shown below is the window for Carbon Copy Cloner, one of several programs that can make bootable clones of your system drive (any drive can be cloned of course).
Select your existing drive (“Source Disk”) and select the new drive (“Target Disk”), then click thebutton. The process will take time proportional to how much data you have on the drives, the speed of each drive, etc. Figure 15 minutes or more in most cases.
As shown below, the boot volume Boot is being cloned to BootClone (I append the date and time to my clones, which is optional, just something I prefer).