Mission Control received a bit of a makeover with OS X El Capitan. On the surface, it looks and acts roughly the same, shrinking your open windows into thumbnails and providing a glimpse and quick access to your other desktop spaces in an effort to help multitaskers make order of a crowded Mac. There are, however, a few important differences.
The gesture to access Mission Control remains the same. Depending on how you have your trackpad preferences set, you can swipe up with three or four fingers to call up Mission Control.
The big difference you'll see is the thumbnails are displayed in a single layer -- no longer are multiple windows of the same app stacked on top of one another. This makes it easier to see your many open windows in Chrome or Safari, for example, but it can make it more difficult to locate a particular thumbnail.
Also making it harder to make sense of a cluttered Mission Control array of thumbnails are the absence of app labels. Before, each thumbnail window got its own app icon, making it easy to see where each of your open apps was located in Mission Control. With El Capitan, a text label appears only when you mouse over a thumbnail. And it doesn't always show the app's name; Chrome and Safari thumbnails, for example, show the page title of the current tab.
One change that might help you quickly locate an app in Mission Control is the fact that app thumbnails are positioned relative to their window's location on your desktop.
Another change is the desktop spaces in the banner at the top of the screen are displayed only as text labels. You won't see the desktop thumbnails until you mouse over the banner. This arrangement lends more space to the app thumbnails in the main area of Mission Control.
For more, get all you need to know about OS X El Capitan.