Syncing with iCloud
Once you've set up iCloud on all of your devices, you can begin using it. For example, take a few photos on your iPhone, then exit the Camera app. As soon as your device is connected to Wi-Fi, your photos will be pushed to all of your other devices. If you've enabled automatic downloads, you can also begin purchasing music or TV shows, and they'll appear on your devices right away.
Although most iCloud features happen automatically, the backup feature only happens when your iOS device meets certain conditions. It must be plugged in to a power source (a wall outlet or computer), connected to Wi-Fi, and locked. More than likely, this means the backup will happen when you charge the device at night.
One of the best things about iCloud is the fact that you can view your most important information online, even if you don't have any of your devices with you. Simply go to iCloud.com and sign in with your Apple ID. You'll be able to view your calendar, locate your device, and more right in your web browser.