OS X El Capitan doesn't have a ton of landmark features, which means most of the cool stuff is under the hood. Let's take a look at some of the lesser known features.
Mail Now Supports Tabs
Are you the type of person who likes to write multiple emails at once? Congratulations, El Capitan's new version of Mail makes that a heck of lot easier with tabs. You can now open up new tabs for emails with Command+N just as you would with web browsers, though it only works in fullscreen mode.
Swipe to Delete Emails in Mail
Swipe to Delete for emails on iOS is one of those great little features that pretty much every email app uses nowadays. In El Capitan, you can do that same gesture with your trackpad.
Quickly Add Events to Your Calendar from Mail
As with iOS 9, El Capitan now scans your email for data indicators and can add events and contacts from Mail directly to Calendar with just a click. When it sees a date listed in your email, you'll get a little notification to add it to your calendar if you want.
Track Flights from Anywhere in OS X
Just like in iOS (noticing a theme here?), El Capitan now detects flight numbers. If it sees what it thinks is a flight in Mail, Notes, Messages, or just about anywhere else, it will show a box when you mouse over it. Click on it and you'll get up-to-date info on that flight.
Rename Files from the Contextual Menu
If you're not a fan of "slow-clicking" on a file's name to rename it, you can now do so by right-clicking a file, then selecting "Rename File."
Change App Store Password Settings
If you have a pretty secure setup for your computer, you can now change the setting for how often and when you need to enter in your password to download stuff from the Mac App Store, just like you can with iOS.
Copy a File's Path with a Right-Click
You can now copy a file's full pathname from the contextual menu. Just right-click the file, tap the Option key, and you'll see the option to "Copy Pathname." If you use Terminal a lot, this one is extremely handy.
Show and Hide the Menu Bar
Just like the Dock, you can now easily show and hide the menu bar. Open up System Preferences > General, and check the box marked "Automatically hide and show the menu bar"
File Copy Resume Picks Up Copies Where You Left Off
In previous versions of OS X, when a file copy was interrupted because you lost the connection or your computer went to sleep, you'd have to start all over again. Now, it should automatically resume that copying process when you're back up and running.
AirPlay Videos without Sharing the Full Screen
For whatever reason, the only way to AirPlay web videos out of Safari before El Capitan was to share the whole browser screen. Now, you can tap the AirPlay icon on a video in Safari and pick your device without showing everything else on your desktop.