fdisk -l command shows the disks and a bunch of stats about them, including the partitions.
The disks are generally in the form of /dev/sdx and partitions /dev/sdxn, where x is a letter and n is a number (so sda is the first physical disk and sda1 is the first partition on that disk).
df -h command gives the size and usage stats per partition.
df shows the usage in blocks, with it it’s human readable.
if you are not a super user then you have to use sudo command in-front of the fdisk command.