Bitcoin-QT is ...

Bitcoin-QT is the original Bitcoin wallet with very complete functionality and excellent security if users do not mind the enormous sizenya and the length of time synchronization with Bitcoin network every time it will be used.

This wallet can be downloaded for free but once installed, the wallet will automatically download the entire database of Bitcoin (Blockchain) networks with large data can reach tens of gigabytes. This is why Wallet Bitcoin-QT is rarely recommended for the layman.