The best explanation for the usage purposes for mobile, tablet and laptops I've read was from Google multiscreen report. Here's one page from that report to explain really well the differences.
Of course it's simplification, as all good explanations. Magic with tablet is, that it's not pushing you the connections that mobile and laptops are. At least if you haven't enabled mail, chat and other connection notifications.
Maybe the guys at Apple had all this idea figured out before everyone else. What is certain is, tablet has found its market and it is here to stay.
Written by +Henri Hämäläinen