With Handoff, you can start writing an email on your iPhone or other iOS device and you can pick up where you left off on your Mac; or put together a report in Pages on your Mac and add the finishing touches with your iPad on the train to work.
Extending your notebook’s battery life. Modern Mac notebooks have a very good battery life. Indeed, they should last all day on a single charge. Even so, there comes a time when you’re running low on power and need to keep your MacBook going