What is the RO sufix in the interfaces?

[souzaramon]

Hello, I have a questions about the naming of the interfaces used in the project.

What exactly is the sufix RO, in the article for example, (ArticleData & ArticleRO)

I'm sorry to bother with that, but a literally can not find anything about it

[Mehoff]

My guess, that it is 'Return Object'. But personally, I don't know what is the benefit of covering UserData interface in another interface ( UserRO )