From the official Symbiont press release:

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Symbiont.io is a FinTech company focused on fostering the symbiotic relationship between traditional financial markets and cryptographic blockchain technology. Its efforts will be centered on the creation of SMART SECURITIES: self-executing digital contracts that are stored on a global, shared database called a "blockchain," which no one party controls.

Robby Dermody, co-founder of Counterparty and President of symbiont.io, added: "Since we founded Counterparty over a year ago, our focus has consistently been on the creation and positioning of this technology as a solution for structural issues in the larger financial markets. Symbiont is the next step in achieving that goal."

Source: http://www.prnewswire.com/news-releases/founders-of-bitcoin-20-project-counterparty-team-up-with-mathmoney-fx-to-make-markets-smarter-300047977.html

You CANNOT use self-executing digital contracts without XCP!

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XCP is the fuel for smart contracts. When smart contracts are running, fuel is used for each execution step. Appropriately enough, this fuel is burned (destroyed). This means that the supply of XCP is continously decreasing. However, the cost of fuel adjusts proportionally as the supply of XCP goes down, so that it cannot reach 0.

Source: http://counterparty.io/docs/faq/#why-does-xcp-have-value

Can't be any clearer than this.

Bonus:

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With the Ripple Gateway implementation, Counterparty users will now be able to transfer their funds in real-time with minimal transaction fees.

Symbiont connects XCP to Ripple to enable (almost) instant transactions. Why is this not bigger news? Roll Eyes

http://www.prnewswire.com/news-releases/symbiont-creates-ripple-gateway-for-counterparty-xcp-300058719.html