Difference between Show Documentation (ctrl-shift-space) and Ctrl-drag.

Hi,

When I ctrl-drag on a method, what is being shown? Is that the rdoc? Or 
is it something else. I notice that what I see when I ctrl-drag is 
sometime the same as what I see when I ctrl-shift-space on the same 
method, and sometimes it is not the same. Why is that?

Sometimes ctrl-drag will show output and ctrl-shift-space does not. 
Sometimes it is the other way around. Is there a reason this happens?

When I ctrl-drag and the text is wider or longer than the display box, 
what can I do to see the whole thing?