What does the lock icon mean on a iphone?

I just noticed it today (I've had my iPhone for a year) what does that icon mean? Here's a picture of it (I'm 14)

Its rotation lock. When you turn it on, screen orientation does not change regardless of the position you are holding your phone in. (portrait or landscape)

It means lock, it locks the phone so you can't access it without the password

It's a rotation lock. You know when the screen flips around when you tilt your phone? Yeah, it stops that and locks the screen into it's normal position. Try it out and you'll see what I mean! Hope this helps.

It is Screen Orientation lock / unlock switch. You lock it and the screen won't rotate, unlock it and screen will start rotating when tilted.

Screen rotation lock.

Why does your age matter?

Anyways… That means that your phone is in Portrait lock mode. It won't turn to landscape mode.

Means lock till times.

It stops the screen from rotating when you turn the phone sideways.

It's the screen orientation lock. You know vertical or Horizontal.