What is this container/volume on my disk?

Sorry, I thought you were looking in Disk Utility.

You have an orphaned Data volume that likely came from a reinstall.

In Disk Utility, you should see your current Data volume listed under Apple Volumes

If you select Apple - Data2, it will show a mount point of /Volumes. You an remove it by clicking the Remove Volume button (–)

While it is not likely all of the data did not get transferred, you may want to look into it before removing that volume.

It's your Data. The startup drive is now divided into a System and a Data volume.

There are several others that handle boot, VM, Updates, and Recovery.

Yes, just remove the volume as I explained above. Don’t try to move it to the Trash.

That is all normal.

A sealed snapshot of the system volume is made, and that is what is used to start up the Mac. You see the actual system volume disabled in the snapshot as active.