Wikipedia
Peercoin, also known as PPCoin or PPC, is a peer-to-peer cryptocurrency utilizing both proof-of-stake and proof-of-work systems.
Peercoin is based on an August 2012 paper which listed the authors as Scott Nadal and Sunny King. Sunny King, who also created Primecoin, is a pseudonym. Nadal's involvement had diminished by November 2013, leaving King as Peercoin's sole core developer.
Peercoin was inspired by bitcoin, and it shares much of the source code and technical implementation of bitcoin. The Peercoin source code is distributed under the MIT/ X11 software license.
Peercoin is the fourth largest minable cryptocurrency by market capitalization. Peercoin has a market cap of $30 million USD as of Jul 20, 2014. Unlike bitcoin, Namecoin, and Litecoin, Peercoin does not have a hard limit on the number of possible coins, but is designed to eventually attain an annual inflation rate of 1%. There is a deflationary aspect to Peercoin as the transaction fee of 0.01 PPC/kb paid to the network is destroyed. This feature, along with increased energy efficiency, aim to allow for greater long-term scalability.