If you have already installed the original bitcoin client (Bitcoin Core), then you are running a wallet, but may not even know it. In addition to relaying transactions on the network, this software also enables you to create a bitcoin address for sending and receiving the virtual currency, and to store the private key for it.
There are other desktop wallets too, all with different features. MultiBit runs on Windows, Mac OSX, and Linux. Hive is an OS X-based wallet with some unique features, including an app store that connects directly to bitcoin services.
Some desktop wallets are tailored for enhanced security: Armory falls into this category.
Others focus on anonymity: DarkWallet – uses a lightweight browser plug-in to provide services including coin ‘mixing’ in which users’ coins are exchanged for others’, to prevent people tracking them.
