DISCLAIMER This post reflects my personal opinion only; it does not constitute investment advice of any kind.
Bitcoin was written so that each individual BTC balance is indistinguishable from any other. There is no such thing as my 2 BTC any more than there is my 2 Dollar balance. Bitcoins, just like Dollars, have no indentity.
This is to say that Bitcoins and Dollars and fungible.
But we may wish to use blockchains for keeping track of individual assets such as collectibles (think Cryptokitties) or anything that relates to a real-world entity such as a house or a car.
Some hacks on top of traditional blockchains have been done in order to have that:
ERC721 is an adaptation of the ERC20 protocol for non-fungible assets;
The Counterparty protocol is a second layer protocol on top of the Bitcoin blockchain;
Coloured Coins are various ways to hack non-fungibility into Bitcoins.
These systems are not ideal because the underlying blockchains do not support them natively, among other difficulties.
Ravencoin is a new blockchain - the code for Ravencoin is a fork off Bitcoin Core - whose aim is to provide support for individual, non-fungible tokens, out of the box.
The Raven protocol supports the issuance of assets, which are essentially non-mineable coins that can be issued by anyone, and they are part of transactions the same way a regular token (used for Proof of Work).
Assets can be:
Unique: representing the ownership of a physical/digital object like a car or a digital collectible such as a Pokémon.
Multiple: representing shares of a company, for example.
Token used for incentivizing Proof-of-work validations. It's also needed to issue Assets on the Ravencoin blockchain.
A new Proof-of-work algorithm was designed for the Raven protocol, with the aim of preventing ASIC mining.
Ravencoin was founded by Bruce Fenton.