Notification Center is a way to collect all your widgets and alerts all in one place.
Since its debut in iOS 5, Apple has included first-party widgets, removed them, then added support for third-party widgets. Apple has added a missed tab and then taken it away. Apple has added predictive widgets ? Notification Center can now tell you how long it will take to get to your next likely destination ? but they haven't expanded on the concept. Apple also added Control Center to iOS 7. Instead of bundling toggles sliders, buttons, and shortcuts into the top-down Notification Center, they created a new, separate bottom-up drawer instead.
Full story from the iMore Blog...