difference between ' and "

Hi everybody,

 From my experience (which is limited), it seems to me that ' 
(apostrophe) and " (quotation marks) are the same in R: they are both 
used for strings. The only difference would be taste.
But I've recently read about the difference between = and <- and I 
thought that there might be a difference here too in some cases.
It might also depend on the operating system.

Thanks for your input!
Ivan