Airdrop:
This sharing feature of Apple is enhanced in OS X Yosemite. You can share files between your OS X Yosemite and iOS 8 devices.
iCloud Drive:
In OS X Yosemite the finder window has a new folder called iCloud drive. You can put your files in it and these files can be accessed on all your devices. You can use iCloud.com to access these files on a PC as well.
Mail enhancements:
There a new feature called mail drop in the mail app of OS X Yosemite. It allows you to send large files through mail. The recipient will get a link in the mail body from where they can download the large files via that link.
Safari Updates:
Safari sidebar now has quick links which allows access your favourite website more quickly and efficiently. The new sidebar is better than before and recent view looks fantastic and familiar.
Continuity:
This new features allows to work across the devices. For example, you are working on a keynote presentation on your Mac running OS X Yosemite and you want to continue on your iPad running on iOS 8 you just have to tap on the keynote icon which appears on the corner of the iPad screen and it will open the keynote app on your iPad for you you to continue. For the this feature both devices should be on the same WiFi.
Asking questions are truly nice thing if you are not understanding anything entirely, but this piece
of writing provides good understanding even.