What is the icon that resembles a lock next to the battery icon?

[iMore Question]

On my iphone i have a lock sign beside the battery usage amount in the top right corner, what does this mean?

 

[Beyond Fire]

Thats the rotation lock, you can disable it by opening up control center and tapping on the lock icon.

edit: if your on ios6 or older then open the app switcher and scroll to the left, its by the music controls

 

[Jaguarr40]

If you don't use your phone in landscape mode and only keep it upright in portrait, That is what that lock is used for.

 

[Manoharan Thangavelu]

The reason for that lock icon is The screen rotation or display rotation is locked. Turn it on will do. The lock icon beside the charge level icon will disappear