LocalBitcoins.com emulates the philosophy of the Bitcoin it trades in – it is completely decentralized in that you can trade directly with another person for Bitcoins. There is no central stock-exchange that you need to route your trading through.
LocalBitcoins.com supports every payment method that is available in the community it serves. And the process of using this site is also really simple.
Users post their advertisements on LocalBitcoins.com. In the ad, they announce the exchange rate they want as well as their preferred payment method for the exchange. If you are interested, simply respond to those ads and arrange to purchase Bitcoins directly with him/her.
All Bitcoins being traded are kept in the LocalBitcoins.com web wallet through which you can transact for your Bitcoin buying or selling directly.