This is useful if you don’t want to connect your device to internet every time you want translation or if you are going out where internet connection is too slow or not available. This is also useful if you are going to visit some other country.
According to Google, offline version is not better than online version but it can translate some simple words or phrases that you can use.
If you want you can use your device’s camera to get translation of written words on some board or on page as Google translate can read words in written form with the help of your device’s camera.
Download Google translate from Google Play.