bash – what does start and end refer to in the disk managment on linux


I have started learning basic IT and Disk management on Linux for a program I am writing. I started with the parted tool and when creating a disk it requires start and end values for creating partitions and I don’t understand what start and end refer to.(as you can see below there are start and End columns they are what I refer to)

test@test:~$ sudo parted -l
(sudo) password for test: 
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sda: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type      File system  Flags
 1      1049kB  538MB   537MB   primary   fat32        boot
 2      539MB   21.5GB  20.9GB  extended
 5      539MB   21.5GB  20.9GB  logical   ext4


Model: DiskModel
Disk /dev/sdb: 4005MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags: 

Number  Start   End     Size    Type     File system  Flags
 1      65.5kB  4005MB  4004MB  primary  ntfs         boot

All help is much appreciated, thank you in advance, Yovel.