To understand these, think of them as different projects rather than simple currencies.
All of these started with Bitcoin, the expensive one, the only reason it's expensive is: because it's the most popular and widely accepted cryptocurrency. Since Bitcoin is hard to mine and has its limitations, people created Bitcoin forks (projects derived from Bitcoin), like BitcoinCash (BTC), Litcoin (LTC), SotoshiVision (SV), etc these projects were created for a reason, e.g BitcoinCash was created because of a disagreement with the original Bitcoin protocol, likewise SotoshiVision was created because the developers disagreed with original BitcoinCash protocol. And that's why we have these different coins. (disagreement was about the block size, which makes the other coins easy to mine but is less secure etc...)
The sole purpose of these coins like Bitcoin, BitcoinCash is a decentralized financial system.
Then we come to projects like Ethereum, now Ethereum is different from Bitcoin because it's not a decentralized financial system but rather a decentralized application system, Ethereum is all about creating computer software that are decentralized (dapps). These crypto need blockchains to operate (computer nodes connected together), now a computer node on an Ethereum blockchain works differently than a Bitcoin blockchain node. That's why Ethereum has its own coin Ether (ETH).
Now we come to Ethereum Classic (ETC), Ethereum Classic is the original one (first one) from which Ethereum (ETH) has been forked because of disagreement. ๐
Ethereum has its competitors like Neo, Ada, SOL etc...
Then we have chainlink (LINK) and Pyth which connects different blockchains together and to the outside world.
We have Cosmos (ATOM) whose purpose is to create an Internet of blockchains like the World Wide Web.
And then we have decentralized storage systems like (FIL, Storj, Sia), etc...
A GRT that provides API to dapps. BTT, which is used to get fast service while downloading torrents etc...
So these are all different projects rather than simple currencies.
