What is the differnece between "si" and "iar" - are there times when one should one of these rather than the other?
My opinion as a learner: I feel "iar" suggests a slight contradiction sometimes, but it can be used as "and", too. Right? In english you can use the word "while" instead of "and", when it suggests contradiction.
Not necessarily contradiction but difference. "Eu mănânc pâine iar el mănâncă brânză ". Both are used to link two sentences. You use "iar" or "și" when these are somehow related (like the examples above) and you only use "și" when they are not related ("el e mic și eu mănânc pâine ")