iCloud Backup

Press the button on the top (when held like a book) for a few seconds so it is in sleep mode. The screen is off.

About the buttons and switches on your iPhone, iPad, or iPod touch - https://support.apple.com/kb/HT203017?viewlocale=en_US&locale=en_US

Locked means asleep. You can tap the power/sleep button on the upper right side of your iPad to put your iPad to sleep or to wake it up. Your iPad goes to sleep as well, when you set auto lock for a certain amount of time. Essentially,if your iPad is powered up and the screen is black, it is asleep.