A “Bitcoin Smartphone/App Wallet” is basically the Bitcoin equivalent of a bank account. It allows you to receive bitcoins, store them, and then send them to others.
Smartphone/App Wallets are also great tool to get control over your web wallet with apps. Some of actual just apps are also can be used to send, receive or store bitcoins securely.
You can even try most convenient way by purchasing Bitcoin Hardware Wallet to keep Bitcoins safe and secure.