Posting into streams (Developers Guide)

I wanted some clarifications on creating a stream record, as i'm trying to replicate Creating A Stream in the developers documentation.

I'm trying to follow 'Example: Uploading a new photo', but for a string from my component and not for photo, on line 8 -> $template->setContext( $photoId , 'photos' );
what should replaced by 'photos' for posting a string created by my component in context id?
(in setContext( $ID , '?????');
which contextType we should add??.)

Secondly would Creating a Stream Record be enough or do i also have to create an app?

regards