A very silly silly question (of which I should know the answer)

A very silly silly question (of which I should know the answer)

Actually, there is no such thing as a silly question. We’re all learning here…

I’ve been on G+ since the start, but it has been in fits and starts. Now I am settled in for good. However, there is one thing I’ve not really understood…

Why have the facility to post to the public circle AND  other circles?

What is the point of this? Is there any difference? I suppose it does give you the option of emailing people within that circle (something you obviously can’t do for the public circle).

Which brings me on to another (related) question…

Why do I sometimes get notifications that someone has shared an article with me?

I understand why I have notifications for shared articles that are in my NOTIFY circle (I’ve got notifications switched on for that circle). But why do I sometimes get notifications for other articles from people? These articles don’t mention me in their posts, but they still appear in the notification bar. I assume this is different to the “also notify by email” option.

Thanks!

Ian Anderson Gray