• Math-Based Currency
  A math-based currency, also referred to as a cryptocurrency, is a digital asset with verifiable mathematical properties, similar to how we can reliably verify gold as a substance made of atoms with 79 protons. Math-based currencies exist as digital assets in their own right and can be transferred directly between users (as fiat cash can be) without relying on a centralized protocol operator. XRP exists as a math-based currency on the Ripple protocol.
• Abuse Protection
  The primary function of XRP is to protect the Ripple protocol against denial-of-service (DoS) spam attacks. Since the Ripple protocol is based around a shared ledger of accounts, a malicious attacker could create large amounts of “ledger spam” (such as fake accounts) and “transaction spam” (such as fake transactions) in an attempt to overload the protocol. This could cause the size of the ledger to become unmanageable and interfere with the protocol’s ability to quickly settle legitimate transactions.
• Bridge Currency
  XRP has great value as a bridge currency. Because each gateway’s balances trade as distinct assets within Ripple, the number of potential currency pairings can become quite large. Instead of quoting every possible currency/gateway combination, XRP can serve as a useful bridge currency to enable these transfers. This is possible because if every currency is liquid to XRP, then every currency is liquid to every other currency:

The Ledger and Consensus
The Ripple protocol is, at its core, a shared public database. This database includes a ledger, which serves to track accounts and the balances associated with them. The ledger is a distributed database — a perfect, shared record of accounts, balances, and transactions in the Ripple protocol. It is continually and automatically updated by the Ripple Transaction Protocol (RTXP) so that an identical ledger exists on thousands of servers around the world. At any time, anybody can review the ledger and see a record of all activity on the Ripple protocol. When changes are made to the ledger, computers connected to the Ripple protocol will mutually agree to the changes via a process called consensus. The Ripple protocol reaches consensus globally within seconds of a change being made. The consensus finding process is the engineering breakthrough that allows for fast, secure, and decentralized transaction settlement on the Ripple protocol.

The World’s First Distributed Exchange
No one owns or controls the Ripple protocol. It runs on computers around the world, all working together to continually maintain a perfect, shared record of accounts, balances, and transactions. Distributed networks offer many efficiencies over centralized networks. Because the network is “self-clearing”, it eliminates the need for a centralized network operator (and gets rid of the associated layer of fees). Because there is no single point of failure, distributed networks are more reliable. They also tend to be more secure, due to their open source nature.