What does R-sim mean?

[asdfgjkl]

My Japanese friend gave me an iPhone 5 which he bought from Japan, he said that it is Japan locked Openline via R-sim. And can somebody please explain what he said. Thank you.

P.s. I'm not used to hearing these words so bear with me.

 

[hang-the-9]

Locked or unlocked? R-Sim is a product used to unlock phones. You could have just asked him.