First of all I think Bitcoin is not the mother of all coins, it is more like the King of all coins. It heavily impacts the prices of other coins.
Secondly the reason there are so many coins, is simply because it is much more easier to create them compared to the early days of crypto. Specifically Ethereum has facilitated this growth and now basically anyone with some blockchain and IT knowledge can create their own tokens. And some tools make it even more easier.
Vitalik Buterin is the creator of Ethereum. He used to be active on Bitcointalk also, but that is few years ago. As per him he decided to co-create Ethereum after World of Warcraft (a game) took some abilities from his game character. He basically wanted to create a more decentralized environment, where the rules can't be changed just whenever the creator wants to.
In simple words, Bitcoin only enabled the transfer of funds and Ethereum enabled the transfer of smart contracts along with funds. This basically meant that you can create complex applications on top of thereum which can't be controlled by 1 single entity. These are now known as Dapps that is decentralized apps. Some popular Dapps are cryptokitties, Cent, Lunyr etc.
Since you are new, I explained in very simple terms, but you can always research more if you want to increase your knowledge. It might seem very very complex at first, but you start getting it after consistent efforts. Good luck!
Thanks for giving very helful advised, yes I want to gathered more and more information about the crypto world that is why I made this thread to gathered information to help my self.
If you wish to properly gather information's you need to read more and more. There are
many threads here of forum where you can read about interesting things in crypto-world.
Siddhartha1492 gave you simple explanation about how Ethereum works as a
platform for creating new tokens. Why there are so many of them can also be explained by
a need for coins cause there will be just 21 million Bitcoins, that is not enough for the world.
In that need for more coins platforms like Ethereum gave us smart contracts, now companies
can have their own coin for their own business.
If you really wish to help yourself and learn more about crypto- currencies I suggest you to visit
their official sites and read there what they do and what they plan, only after come here and check
are other people support that and how they look at that project. It is good to know what community
thinks and to check some expert insights.