Bitcoin and others

bitcoin was the first full blockchain based cryptocurrency. so you can say bitcoin was somewhat the original idea to create a decentralized (peer to peer) digital cash or cryptocurrency.

as it grew bigger and gained more fame, since that "idea" was interesting and also since bitcoin has always been open source a lot of new projects were created to explore new ideas. for example Litecoin was created to have faster blocks and a different mining algo. namecoin was created to have a blockchain where you can store data inside its blockchain so to create a decentralized database which can now be used for domain names. there are a lot of different altcoins now, many of which have pretty interesting "new ideas".

at some point people realized that on top of the "idea" being pretty interesting, it can also create a lot of money due to being a "currency". and that led to creation of thousands of copycat coins where they simply copied code from another (still open source) projects and creating their own coins without adding or changing anything of value.

so now we have two groups of altcoins:
1. those with something new to offer which are exploring new potentials of blockchain technology.
2. those which are simply poor copies of the first group which stay around for a while and get pumped and dumped before dying for good.