Yes, but there are complications.
Traditional partitions allow you to have multiple different file systems that could even be different
types (HFS, APFS for Mac, FAT32 or NTFS for Windows, ext3/4 for Linux etc.) on a disk - with a traditional HDD each partition had part of the disk physically dedicated to it (SSDs are somewhat more complicated). Changing the partition layout without wiping the whole disk is possible - but can be complicated and slow as it requires physically moving data around.
APFS added the concept of "Volumes" which look something like partitions to the user, but are quick and easy to create and delete because they're managed by the system keeping track of what data belongs in which volume and don't rely on physical disc locations. With APFS you have a "Container" (think of that as an old-school partition) that can contain multiple APFS "volumes". APFS also has tricks like creating "snapshots" instantly (because nothing has to be duplicated until it actually changes) - modern backup apps will first create an instant "snapshot" of the volume and proceed to back up
that so you can go on working and changing things without interfering with the backup. Then there are "overlay" volumes where one read-only volume contains the original files and another volume just contains the additions and changes.
So what you are seeing is the main "Container"
partition, which contains a set of
volumes called "Macintosh HD". The further complication are that what you normally see as "Macintosh HD" is actually - as
@NoBoMac said - the volume "Macintosh HD - Data" with your files and changes overlayed on the immutable "Macintosh HD" volume containing the system files.
So, TL
NR is that the your stuff that needs backing up is in the "Macintosh HD" - but let your backup utility worry about that.
As long as you're working in an all-APFS world, Volumes are ideal for this. They're also useful if you want to share a disk between Time Machine and other backups.
Well, in an ideal world you'd use both for redundancy. One copy is not a backup - the "321" rule is 3 backups, 2 different formats, 1 off site".
Maybe Time Machine for day-to-day and CCC or Super Duper once a week or something (NB: do what I say, don't do what I do
). Time Machine is easy and convenient but has been known to foul up - especially if you're using it with a NAS.
Also, there are some types of file (large media files, virtual machine disk images) that you want a backup copy of but
don't need a file history for. There's a bunch of stuff on my HD excluded from time machine for which an occasional snapshot is fine.
