Most cryptocoin mining requires specialized hardware, but Peercoin minting can be done on any computer. Minting is energy-efficient, because it is based on the Peercoins you hold, rather than on your processing power.
Each time your minting generates a block, your coins help guard the network. To reliably attack the Peercoin network, a malicious user must control the majority of all minting coins, which could even end up harming his own investment.
Minting earns you 1% annually. Coins are first eligible to mint 30 days after they have been transferred, and after 90 days, their chance of success is maximized. If you mint more often, your earnings will compound!