List Disks, Partitions and Filesystems in Ubuntu

The one I use most:

sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL

Other useful ones:

lsblk -f          # filesystems, UUIDs and mount points
df -hT            # used/free space per mounted filesystem
sudo blkid        # UUIDs and filesystem types
sudo fdisk -l     # partition tables and real disk sizes
findmnt           # mount tree

More info.

Related: add a new disk and extend a disk.