Now that you have the app downloading, I can bore (not really) you with the details.
- Interact with the Bitcoin network directly from your phone, without any third-party gateway or services.
- When no internet connection is available, transactions initiated will be queued until a connection is established.
- Receive and send Bitcoins via QR codes, as well as any link using the Bitcoin URI format.
- Wallet.dat is backed up and stored in the cloud, inside your Google account's storage.
- Stores only the block headers locally (SD card) and implements "Simplified Payment Verification" as described by Satoshi Nakamoto in his Bitcoin Paper.
Bitcoin for Android is an open source project and the (original) labor of Brian Armstrong, you can check out the bitcoin-android project on Github.