Hi Rahul,
Welcome to THG forumz.
Remember, a hardware is an actual physical piece of technology, like a circuit board, a processor chip, a memory chip, etc. The CMOS is that hardware which is used when the computer first comes on. It is from this CMOS that the computer "discovers" itself.
A software is programming code that allows the user(or other pieces of software or hardware) to interact with the hardware. Any example of this is a driver that allows an operating system to work with a sound card, or an operating system that allows the user to interact with the hard drive. Most software we use today is stored on discs, but software can be stored on chips (hardware). The BIOS is such a piece of software. It is stored on the CMOS and is designed to be Read-Only. We call this type of storage ROM (Read-Only Memory). It is important to note that the BIOS can be edited, after a fashion, by "flashing". That is to say, the BIOS can be replaced by a different version, but it cannot be edited in the same way that you edit the settings on Firefox, or determine the installation location of you favorite game.
By the way, if I am in error on my technical details, please do not flame me; I am not an expert like a lot of the forum veterans (but I do aspire to be, one day).