Difference between boot disk, boot drive, and boot volume

in disk utility, what is the boot drive, boot volume, and boot disk? I'm follosing instructions for restarting my Mac in recovery mode and the instructions say to:

"1. Reboot your Mac and hold Command-R at startup to enter Recovery Mode.

2. Open Disk Utility at the OS X Tools window.

3. Select your boot drive and boot disk on the sidebar.

4. Click Disk Utility’s “Repair Disk” button in the First Aid tab.

After performing these routines to fix your drive’s partition scheme and formatting, use Disk Utility to perform a permissions fix on your boot volume (this is in the same First Aid tab). Then shut down your Mac (do not reboot it), and perform an SMC reset (see here) and PRAM reset (see here) for good measure."

This is what I'm seeing in my disk utility:

Which of these is the boot drive, boot volume, and boot disk?