In case you're new from Windows I want to explain about the Linux way of numbering disks and partitions before you get too confused and upset. There's no such thing as a 'C: drive' in Linux or any other drive letter for that matter. I hope you'll see why the Linux partition naming system makes a lot more sense.
In Linux the word 'disk' means an entire disk, such as a hard disk drive, SSD or flash memory drive.
Disks are numbered with letters, starting with 'a' for the first disk and 'b' for the second and so on.
Partitions have numbers.
Only primary partitions including the extended partition if there is one can have the numbers 1, 2, 3 or 4.
Logical partitions (inside the extended) are always numbered counting from 5 upwards.
If you're not sure what I'm talking about here and you're curious you may use this link, Help on Partitioning.
If you look in the screencap below, you'll see a spinbox over in the top right-hand corner for changing between one hard disk and another, including and USB drives you may have plugged in.
My first disk is called /dev/sda in Linux speak.
My second disk is called /dev/sdb.
My third disk will be called '/dev/sdc', and so on ...
The first part, '/dev/' stands for 'device', and the second part, 'sda', means hard drive 'a', for the first hard drive.
It used to be 'hda' in the old days, for 'hard drive a', but they changed the 'h' to an 's' for reasons that are outside the scope of this how-to.
The first partition in my /dev/sda disk is /dev/sda1.
The second partition is called /dev/sda2.
If I had more partitions they'd be numbered /dev/sda3, and /dev/sda4.
Partitions don't necessarily need to appear on the disk arranged in numerical order.