What does it mean to mount sda3 on /dev?

Question

I am asking this question after searching a lot on Internet.

I am using linux on my PC. It has a disk which has 3 partitions. sda1, sda2, sda3. sda3 contains linux, sda2 is swap and sda1 is FAT.

My question is that "sda3" is a partition which contains whole when linux than I don't understand what do you mean by mounting it on /dev/sda3?

/home, /usr, /var everything is inside sda3 then why are we saying that we are mounting sda3 on /dev while /dev and all the other filesystems are in sda3?

Answer 1

/dev is a directory containing ''pointers'' (in the form of block/character special files) that give the user/programs access to special devices that only the kernel has access to normally.

sda3 isn't actually mounted on /dev/sda3, that's just the block special file that lets us manipulate sda3. The real ''mount point'' is /.

Answer 2

I found my answer after reading http://en.wikipedia.org/wiki/Device_file

/dev/sda3 is actually a device file.