Have you ever been using your iPhone or iPad and then once you get home or to your office then want to pick up where you left off on your Mac. Well this is really easy now using handoff, this is what is known as continuity. You can be browsing the net, using email, calendar, or one of the apps like Pages and what you are doing transfers to your Mac, it can work the other way to and also between devices like going from your iPhone to your iPad.
This has all come about with iOS8 and OS X Yosemite. If you have these then all you need to do is set them up.
There is also another nice new feature called Instant Hotspot, if you do not have wifi on your Mac or iPad then it can automatically connect to the internet using your iPhone or iPad if your iPad has mobile connectivity. It is a lot easier and faster, you no longer need to turn on personal hotspot in your settings on the mobile device.
Here is video showing you how.